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Title: Structural And Magnetic Properties Of Two Branches Of The Tripod-kagome-lattice Family A(2)r(3)sb(3)o(14) (a = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb).
Creator: Dun, Z. L., Trinh, J., Lee, M., Choi, E. S., Li, K., Hu, Y. F., Wang, Y. X., Blanc, N., Ramirez, A. P., Zhou, H. D.
Abstract/Description: We present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A(2)R(3)Sb(3)O(14) (A= Mg, Zn; R= Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016)]. The present susceptibility (chi(dc), chi(ac)) and specific-heat measurements reveal various magnetic...
Show moreWe present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A(2)R(3)Sb(3)O(14) (A= Mg, Zn; R= Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016)]. The present susceptibility (chi(dc), chi(ac)) and specific-heat measurements reveal various magnetic ground states, including the nonmagnetic singlet state for MgPr, ZnPr; long-range orderings (LROs) for MgGd, ZnGd, MgNd, ZnNd, and MgYb; a long-range magnetic charge ordered state for MgDy, ZnDy, and potentially for MgHo; possible spin-glass states for ZnEr, ZnHo; the absence of spin ordering down to 80 mK for MgEr, MgTb, ZnTb, and ZnYb compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in MgHo, MgTb, and ZnTb can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies, and non-Kramers nature of single-ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger R ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller R ions (Ho, Er, Yb).
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Date Issued: 2017-03-30
Identifier: FSU_libsubv1_wos_000399139000002, 10.1103/PhysRevB.95.104439
Format: Citation

Title: Planar Tunneling Spectroscopy Of The Topological Kondo Insulator Smb6.
Creator: Sun, L., Kim, D.-J., Fisk, Z., Park, W. K.
Abstract/Description: Several technical issues and challenges are identified and investigated for the planar tunneling spectroscopy of the topological Kondo insulator SmB6. Contrasting behaviors of the tunnel junctions prepared in two different ways are analyzed and explained in detail. The conventional approach based on an AlOx tunnel barrier results in unsatisfactory results due to the interdiffusion between SmB6 and deposited Al. On the contrary, plasma oxidation of SmB6 crystals produces high-quality tunnel...
Show moreSeveral technical issues and challenges are identified and investigated for the planar tunneling spectroscopy of the topological Kondo insulator SmB6. Contrasting behaviors of the tunnel junctions prepared in two different ways are analyzed and explained in detail. The conventional approach based on an AlOx tunnel barrier results in unsatisfactory results due to the interdiffusion between SmB6 and deposited Al. On the contrary, plasma oxidation of SmB6 crystals produces high-quality tunnel barriers on both (001) and (011) surfaces. Resultant conductance spectra are highly reproducible with clear signatures for the predicted surface Dirac fermions and the bulk hybridization gap as well. The surface states are identified to reside on two or one distinguishable Dirac cone(s) on the (001) and (011) surface, respectively, in good agreement with the recent literature. However, their topological protection is found to be limited within the low energy region due to their inevitable interaction with the bulk excitations, called spin excitons, consistent with a recent theoretical prediction. Implications of our findings on other physical properties in SmB6 and also other correlated topological materials are remarked.
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Date Issued: 2017-05-15
Identifier: FSU_libsubv1_wos_000401449700001, 10.1103/PhysRevB.95.195129
Format: Citation

Title: Magnetic Properties Of The Triangular Lattice Magnets A(4)b ' B2o12 (a=ba, Sr, La; B '=co, Ni, Mn; B=w, Re).
Creator: Rawl, R., Lee, M., Choi, E. S., Li, G., Chen, K. W., Baumbach, R., dela Cruz, C. R., Ma, J., Zhou, H. D.
Abstract/Description: The geometrically frustrated two-dimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by x-ray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specific-heat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin-1/2) and Ni2+ (spin-1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin-5/2) ions...
Show moreThe geometrically frustrated two-dimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by x-ray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specific-heat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin-1/2) and Ni2+ (spin-1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin-5/2) ions with a large spin number exhibits antiferromagnetic (AFM) ordering. We ascribe these spin-number-manipulated ground states to the competition between the AFM B'-O-O-B' and FM B'-O-B-O-B' superexchange interactions. (ii) The chemical pressure introduced into the Co-containing samples through the replacement of different-size ions on the A site finely tunes the FM behavior temperature of the system. This effect is not simply governed by the lattice parameters and requires more precise structural measurements to elucidate.
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Date Issued: 2017-05-25
Identifier: FSU_libsubv1_wos_000401998500003, 10.1103/PhysRevB.95.174438
Format: Citation

Title: Forbidden Coherent Transfer Observed Between Two Realizations Of Quasiharmonic Spin Systems.
Creator: Bertaina, S., Yue, G., Dutoit, C.-E., Chiorescu, I.
Abstract/Description: The multilevel system Mn-55(2 vertical bar) is used to generate two pseudoharmonic level systems, as representations of the same electronic sextuplet at different nuclear spin projections. The systems are coupled using a forbidden nuclear transition induced by the crystalline anisotropy. We demonstrate Rabi oscillations between the two representations in conditions similar to two coupled pseudoharmonic quantum oscillators. Rabi oscillations are performed at a detuned pumping frequency which...
Show moreThe multilevel system Mn-55(2 vertical bar) is used to generate two pseudoharmonic level systems, as representations of the same electronic sextuplet at different nuclear spin projections. The systems are coupled using a forbidden nuclear transition induced by the crystalline anisotropy. We demonstrate Rabi oscillations between the two representations in conditions similar to two coupled pseudoharmonic quantum oscillators. Rabi oscillations are performed at a detuned pumping frequency which matches the energy difference between electronuclear states of different oscillators. We measure a coupling stronger than the decoherence rate to indicate the possibility of fast information exchange between the systems.
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Date Issued: 2017-07-20
Identifier: FSU_libsubv1_wos_000405913900004, 10.1103/PhysRevB.96.024428
Format: Citation

Title: Possible Devil's Staircase In The Kondo Lattice Cesbse.
Creator: Chen, K.-W., Lai, Y., Chiu, Y.-C., Steven, S., Besara, T., Graf, D., Siegrist, T., Albrecht-Schmitt, T. E., Balicas, L., Baumbach, R. E.
Abstract/Description: The temperature- (T) magnetic-field (H) phase diagram for the tetragonal layered compound CeSbSe is determined from magnetization, specific heat, and electrical resistivity measurements. This system exhibits complex magnetic ordering at T-M = 3 K and the application of a magnetic field results in a cascade of magnetically ordered states for H less than or similar to 1.8 T which are characterized by fractional integer size steps: i.e., a possible devil's staircase is observed. Electrical...
Show moreThe temperature- (T) magnetic-field (H) phase diagram for the tetragonal layered compound CeSbSe is determined from magnetization, specific heat, and electrical resistivity measurements. This system exhibits complex magnetic ordering at T-M = 3 K and the application of a magnetic field results in a cascade of magnetically ordered states for H less than or similar to 1.8 T which are characterized by fractional integer size steps: i.e., a possible devil's staircase is observed. Electrical transport measurements show a weak temperature dependence and large residual resistivity which suggest a small charge-carrier density and strong scattering from the f moments. These features reveal Kondo lattice behavior where the f moments are screened incompletely, resulting in a fine balanced magnetic interaction between different Ce neighbors that is mediated by the Ruderman-Kittel-Kasuya-Yosida interaction. This produces the nearly degenerate magnetically ordered states that are accessed under an applied magnetic field.
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Date Issued: 2017-07-17
Identifier: FSU_libsubv1_wos_000405697200002, 10.1103/PhysRevB.96.014421
Format: Citation

Title: Decoherence In Semiconductor Nanostructures With Type-ii Band Alignment: All-optical Measurements Using Aharonov-bohm Excitons.
Creator: Kuskovsky, I. L., Mourokh, L. G., Roy, B., Ji, H., Dhomkar, S., Ludwig, J., Smirnov, D., Tamargo, M. C.
Abstract/Description: We examine the temperature dependence of the visibility of the excitonic Aharonov-Bohm peak in type-II quantum dots. We obtain a functional temperature dependence that is similar to that determined by transport experiments, namely, with the T-1 term due to electron-electron collisions and the T-3 term due to electronphonon interactions. However, the magnitude of the latter term is much smaller than that for the transport electrons and similar to the interaction strength of the exciton-phonon...
Show moreWe examine the temperature dependence of the visibility of the excitonic Aharonov-Bohm peak in type-II quantum dots. We obtain a functional temperature dependence that is similar to that determined by transport experiments, namely, with the T-1 term due to electron-electron collisions and the T-3 term due to electronphonon interactions. However, the magnitude of the latter term is much smaller than that for the transport electrons and similar to the interaction strength of the exciton-phonon coupling. Such suppressed electron-phonon interaction ushers a way for all-optical studies of decoherence processes in semiconductor nanostructures as other dephasing mechanisms become more pronounced.
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Date Issued: 2017-04-26
Identifier: FSU_libsubv1_wos_000400064400006, 10.1103/PhysRevB.95.165445
Format: Citation

Title: Hybridization Gap In The Heavy-fermion Compound Upd2al3 Via Quasiparticle Scattering Spectroscopy.
Creator: Jaggi, N. K., Mehio, O., Dwyer, M., Greene, L. H., Baumbach, R. E., Tobash, P. H., Bauer, E. D., Thompson, J. D., Park, W. K.
Abstract/Description: We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd2Al3: Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature andmagnetic field and analyzed using a theory of cotunneling into anAnderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi...
Show moreWe present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd2Al3: Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature andmagnetic field and analyzed using a theory of cotunneling into anAnderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 +/- 0.3meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While the hybridization gap is extrapolated to remain finite up to similar to 28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at similar to 18 K, slightly above the antiferromagnetic transition temperature (T-N approximate to 14 K). This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance is greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd2Al3.
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Date Issued: 2017-04-17
Identifier: FSU_libsubv1_wos_000399799500004, 10.1103/PhysRevB.95.165123
Format: Citation

Title: Entanglement Entropy And Topological Order In Resonating Valence-bond Quantum Spin Liquids.
Creator: Wildeboer, Julia, Seidel, Alexander, Melko, Roger G.
Abstract/Description: On the triangular and kagome lattices, short-ranged resonating valence-bond wave functions can be sampled without the sign problem using a recently developed Pfaffian Monte Carlo scheme. In this Rapid Communication, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with. gamma = ln( 2), as...
Show moreOn the triangular and kagome lattices, short-ranged resonating valence-bond wave functions can be sampled without the sign problem using a recently developed Pfaffian Monte Carlo scheme. In this Rapid Communication, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with. gamma = ln( 2), as expected for a gapped Z(2) quantum spin liquid. We prove that the mutual statistics is consistent with the toric code anyon model and rule out any other quasiparticle statistics such as the double semion model.
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Date Issued: 2017-03-06
Identifier: FSU_libsubv1_wos_000396000700001, 10.1103/PhysRevB.95.100402
Format: Citation

Title: Effects Of Uniaxial Pressure On The Quantum Tunneling Of Magnetization In A High-symmetry Mn-12 Single-molecule Magnet.
Creator: Atkinson, James H., Fournet, Adeline D., Bhaskaran, Lakshmi, Myasoedov, Yuri, Zeldov, Eli, del Barco, Enrique, Hill, Stephen, Christou, George, Friedman, Jonathan R.
Abstract/Description: The symmetry of single-molecule magnets dictates their spin quantum dynamics, influencing how such systems relax via quantum tunneling of magnetization (QTM). By reducing a system's symmetry, through the application of a magnetic field or uniaxial pressure, these dynamics can be modified. We report measurements of the magnetization dynamics of a crystalline sample of the high-symmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH single-molecule magnet as a function of uniaxial pressure...
Show moreThe symmetry of single-molecule magnets dictates their spin quantum dynamics, influencing how such systems relax via quantum tunneling of magnetization (QTM). By reducing a system's symmetry, through the application of a magnetic field or uniaxial pressure, these dynamics can be modified. We report measurements of the magnetization dynamics of a crystalline sample of the high-symmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH single-molecule magnet as a function of uniaxial pressure applied either parallel or perpendicular to the sample's "easy" magnetization axis. At temperatures between 1.8 and 3.3 K, magnetic hysteresis loops exhibit the characteristic steplike features that signal the occurrence of QTM. After applying uniaxial pressure to the sample in situ, both the magnitude and field position of the QTM steps changed. The step magnitudes were observed to grow as a function of pressure in both arrangements of pressure, while pressure applied along (perpendicular to) the sample's easy axis caused the resonant-tunneling fields to increase (decrease). These observations were compared with simulations in which the system's Hamiltonian parameters were changed. From these comparisons, we determined that parallel pressure induces changes to the second-order axial anisotropy parameter as well as either the fourth-order axial or fourth-order transverse parameter, or to both. In addition, we find that pressure applied perpendicular to the easy axis induces a rhombic anisotropy E approximate to D/2000 per kbar that can be understood as deriving from a symmetry-breaking distortion of the molecule.
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Date Issued: 2017-05-04
Identifier: FSU_libsubv1_wos_000400657600001, 10.1103/PhysRevB.95.184403
Format: Citation

Title: Landau-level Spectroscopy Of Massive Dirac Fermions In Single-crystalline Zrte5 Thin Flakes.
Creator: Jiang, Y., Dun, Z. L., Zhou, H. D., Lu, Z., Chen, K.-W., Moon, S., Besara, T., Siegrist, T. M., Baumbach, R. E., Smirnov, D., Jiang, Z.
Abstract/Description: We report infrared magnetospectroscopy studies on thin crystals of an emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure of the Landau-level transitions and zero-field infrared absorption indicate a two-dimensional Dirac-like electronic structure, similar to that in graphene but with a small relativistic mass corresponding to a 9.4-meV energy gap. Measurements with circularly polarized light reveal a significant electron-hole asymmetry, which leads to splitting of...
Show moreWe report infrared magnetospectroscopy studies on thin crystals of an emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure of the Landau-level transitions and zero-field infrared absorption indicate a two-dimensional Dirac-like electronic structure, similar to that in graphene but with a small relativistic mass corresponding to a 9.4-meV energy gap. Measurements with circularly polarized light reveal a significant electron-hole asymmetry, which leads to splitting of the Landau-level transitions at high magnetic fields. Our model, based on the Bernevig-Hughes-Zhang effective Hamiltonian, quantitatively explains all observed transitions, determining the values of the Fermi velocity, Dirac mass (or gap), electron-hole asymmetry, and electron and hole g factors.
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Date Issued: 2017-07-05
Identifier: FSU_libsubv1_wos_000405026300001, 10.1103/PhysRevB.96.041101
Format: Citation

Title: Transport, magnetic, and optical properties of electrochemically doped poly(1, 4-dimethoxy phenylene vinylene).
Creator: Schlenoff, Joseph B., Obrzut, Jan, Karasz, F.
Abstract/Description: A coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4- dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an...
Show moreA coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4- dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an applied potential of 3.9 V. Potentials in excess of 3.9 V cause an irreversible decrease in conductivity. Spin and charge show a 1:1 relation on/y to very low doping levels. Two paramagnetic species are produced on doping. A maximum spin concentration is observed at =3.7 V. The ultraviolet —visible —near-infrared spectra of doped PDMPV show at least five absorption bands, at 4.8, 3.7, 2.5, 1.7, and 0.6 eV. The first three bands decrease with doping and the latter two increase. When analyzed by the polaron or bipolaron model, the optical data imply significant symmetry breaking, Contributions to the optical activity from polarons and bipolarons are determined from the EPR results and are found to be di6'erent for both peaks, implying greater symmetrybreaking eA'ects for polarons. An electrochemical analysis of EPR results suggests that polaron interaction energies are =0.4S eV greater than those for bipolarons.
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Date Issued: 1989
Identifier: FSU_migr_chm_faculty_publications-0006
Format: Citation

$Acoustic wave absorption as a probe of dynamical geometrical response of fractional quantum Hall liquids$

Title: Acoustic wave absorption as a probe of dynamical geometrical response of fractional quantum Hall liquids.
Creator: Yang, Kun
Abstract/Description: We show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a two-dimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intra-Landau level dynamical response in the long-wavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We...
Show moreWe show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a two-dimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intra-Landau level dynamical response in the long-wavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We show that such time-dependent metric (generated by acoustic wave) couples to collective modes of the system, including a quadrapolar mode at long wavelength, and magnetoroton at finite wavelength. Energies of these modes can be revealed in spectroscopic measurements, controlled by strain-induced Fermi velocity anisotropy. We argue that such geometrical probe provides a potentially highly useful alternative probe of quantum Hall liquids, in addition to the usual electromagnetic response.
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Date Issued: 2016-04-15
Identifier: FSU_libsubv1_wos_000374297500001, 10.1103/PhysRevB.93.161302
Format: Citation

Title: Magnetoinfrared spectroscopic study of thin Bi2Te3 single crystals.
Creator: Tung, L.-C., Yu, W., Cadden-Zimansky, P., Miotkowski, I., Chen, Y. P., Smirnov, D., Jiang, Z.
Abstract/Description: Thin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stacked-slab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/- 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following...
Show moreThin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stacked-slab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/- 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following ways: (1) Field-induced transfer of the optical weight from the lower-frequency regime (< 250 cm(-1)) to the higher-frequency regime (> 250 cm(-1)) due to the redistribution of charge carriers across the Fermi surface. (2) Evolving of a Fano-resonance-like spectral feature from an antiresonance to a resonance with increasing magnetic field. Such behavior can be attributed to the electron-phonon interactions between the E-u(1) optical phonon mode and the continuum of electronic transitions. (3) Cyclotron resonance resulting from the intervalence band Landau level transitions, which can be described by the electrodynamics of massive Dirac holes.
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Date Issued: 2016-02-29
Identifier: FSU_libsubv1_wos_000371398500002, 10.1103/PhysRevB.93.085140
Format: Citation

Title: Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe.
Creator: Yakunin, M. V., Suslov, A. V., Popov, M. R., Novik, E. G., Dvoretsky, S. A., Mikhailov, N. N.
Abstract/Description: We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage V-g. This large overlap manifests itself in a much higher critical field B-c separating the range above it with a plain behavior of the Hall...
Show moreWe present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage V-g. This large overlap manifests itself in a much higher critical field B-c separating the range above it with a plain behavior of the Hall magnetoresistance rho(xy) (B), where the quantum peculiarities shift linearly with V-g, and the range below with a complicated behavior. In the latter case, specific structures in rho(xy) (B) are formed like a double-N-shaped rho(xy) (B), reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative V-g as revealed (i) from fits to the low-field N-shaped rho(xy) (B), (ii) from the Fourier analysis of oscillations in rho(xx) (B), and (iii) from a specific behavior of rho(xy) (B) at high positive V-g. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated V-g while the hole density p drops down from the value a factor of 6 larger than n at extreme negative V-g to almost zero at extreme positive V-g passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an oscillating behavior of the valence subband top versus field due to lateral maxima in the energy spectrum, (ii) a reduced gap between the lowest-electron and the highest-hole magnetic levels where the electron- and hole-type localized states are superposed, and (iii) a possible formation of the interlayer electron-hole excitons.
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Date Issued: 2016-02-12
Identifier: FSU_libsubv1_wos_000370025100005, 10.1103/PhysRevB.93.085308
Format: Citation

Title: Melting Of Wigner Crystal In High-mobility N-gaas/algaas Heterostructures At Filling Factors 0.18 > Nu > 0.125: Acoustic Studies.
Creator: Drichko, I. L., Smirnov, I. Yu, Suslov, A. V., Galperin, Y. M., Pfeiffer, L. N., West, K. W.
Abstract/Description: By using acoustic methods the complex high-frequency conductance of high-mobility n-GaAs/AlGaAs heterostructures was determined in magnetic fields 12-18 T. Based on the observed frequency and temperature dependences, we conclude that in the investigated magnetic field range and at sufficiently low temperatures, T less than or similar to 200 mK, the electron system forms a Wigner crystal deformed due to pinning by disorder. At some temperature, which depends on the electron filling factor, the...
Show moreBy using acoustic methods the complex high-frequency conductance of high-mobility n-GaAs/AlGaAs heterostructures was determined in magnetic fields 12-18 T. Based on the observed frequency and temperature dependences, we conclude that in the investigated magnetic field range and at sufficiently low temperatures, T less than or similar to 200 mK, the electron system forms a Wigner crystal deformed due to pinning by disorder. At some temperature, which depends on the electron filling factor, the temperature dependences of both components of the complex conductance get substantially changed. We have ascribed this rapid change of the conduction mechanism to melting of the Wigner crystal and study the dependence of the so-defined melting temperature on the electron filling factor.
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Date Issued: 2016-08-15
Identifier: FSU_libsubv1_wos_000381482600007, 10.1103/PhysRevB.94.075420
Format: Citation

Title: Magnetochromic Sensing And Size-dependent Collective Excitations In Iron Oxide Nanoparticles.
Creator: O'Neal, Kenneth R., Patete, Jonathan M., Chen, Peng, Nanavati, Ruhani, Holinsworth, Brian S., Smith, Jacqueline M., Marques, Carlos, Simonson, Jack W., Aronson, Meigan C.,...
Show moreO'Neal, Kenneth R., Patete, Jonathan M., Chen, Peng, Nanavati, Ruhani, Holinsworth, Brian S., Smith, Jacqueline M., Marques, Carlos, Simonson, Jack W., Aronson, Meigan C., McGill, Stephen A., Wong, Stanislaus S., Musfeldt, Janice L.
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Abstract/Description: We combine optical and magneto-optical spectroscopies with complementary vibrational and magnetic property measurements to reveal finite length scale effects in nanoscale alpha-Fe2O3. Analysis of the d-to-d on-site excitations uncovers enhanced color contrast at particle sizes below approximately 75 nm due to size-induced changes in spin-charge coupling that are suppressed again below the superparamagnetic limit. These findings provide a general strategy for amplifying magnetochromism in...
Show moreWe combine optical and magneto-optical spectroscopies with complementary vibrational and magnetic property measurements to reveal finite length scale effects in nanoscale alpha-Fe2O3. Analysis of the d-to-d on-site excitations uncovers enhanced color contrast at particle sizes below approximately 75 nm due to size-induced changes in spin-charge coupling that are suppressed again below the superparamagnetic limit. These findings provide a general strategy for amplifying magnetochromism in alpha-Fe2O3 and other iron-containing nanomaterials that may be useful for advanced sensing applications. We also unravel the size dependence of collective excitations in this iconic antiferromagnet.
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Date Issued: 2017-03-10
Identifier: FSU_libsubv1_wos_000396013400006, 10.1103/PhysRevB.95.125416
Format: Citation

Title: Magnetic Ground States And Magnetodielectric Effect In Rcr(bo3)(2) (r = Y And Ho).
Creator: Sinclair, R., Zhou, H. D., Lee, M., Choi, S., Li, G., Hong, T., Calder, S.
Abstract/Description: The layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 8-9 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 2-3 T is applied below TN, the Cr3+...
Show moreThe layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 8-9 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 2-3 T is applied below TN, the Cr3+ spins in the Y compound and both the Cr3+ and Ho3+ spins in the Ho compound order in a ferromagnetic state; (iii) both samples exhibit dielectric constant anomalies around the transition temperature and critical field, but the Ho compound displays a much stronger magnetodielectric response. We speculate that this is due to the magnetostriction, which depends on both the Cr3+ and the Ho3+ ions' ordering in the Ho compound. Moreover, by using linear spin-wave theory to simulate the inelastic neutron scattering data, we estimated the Y compound's intralayer and interlayer exchange strengths as ferromagnetic J(1) = -0.12 meV and antiferromagnetic J(2) = 0.014 meV, respectively. The competition between different kinds of superexchange interactions results in the ferromagnetic intralayer interaction.
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Date Issued: 2017-05-08
Identifier: FSU_libsubv1_wos_000401223700002, 10.1103/PhysRevB.95.174410
Format: Citation

Title: Magnetic Phases Of The Quasi-two-dimensional Antiferromagnet Cucro2 On A Triangular Lattice.
Creator: Sakhratov, Yu A., Svistov, L. E., Kuhns, P. L., Zhou, H. D., Reyes, A. P.
Abstract/Description: We have carried out Cu-63,Cu-65 NMR spectra measurements in a magnetic field up to about 45 T on a single crystal of a multiferroic triangular antiferromagnet CuCrO2. The measurements were performed for magnetic fields aligned along the crystal c axis. Field and temperature evolution of the spectral shape demonstrates a number of phase transitions. It was found that the 3D magnetic ordering takes place in the low field range (H less than or similar to 15 T). At higher fields magnetic...
Show moreWe have carried out Cu-63,Cu-65 NMR spectra measurements in a magnetic field up to about 45 T on a single crystal of a multiferroic triangular antiferromagnet CuCrO2. The measurements were performed for magnetic fields aligned along the crystal c axis. Field and temperature evolution of the spectral shape demonstrates a number of phase transitions. It was found that the 3D magnetic ordering takes place in the low field range (H less than or similar to 15 T). At higher fields magnetic structures form within individual triangular planes whereas the spin directions of the magnetic ions from neighboring planes are not correlated. It is established that the 2D-3D transition is hysteretic in field and temperature. Line-shape analysis reveals several possible magnetic structures existing within individual planes for different phases of CuCrO2. Within certain regions on the magnetic H-T phase diagram of CuCrO2 a 3D magnetic ordering with tensor order parameter is expected.
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Date Issued: 2016-09-12
Identifier: FSU_libsubv1_wos_000383138700003, 10.1103/PhysRevB.94.094410
Format: Citation

Title: Non-ising-like Two-dimensional Superconductivity In A Bulk Single Crystal.
Creator: Zhang, Q. R., Rhodes, D., Zeng, B., Johannes, M. D., Balicas, L.
Abstract/Description: Both Nb3PdxSe7 and Ta4Pd3Te16 crystallize in a monoclinic point group while exhibiting superconducting transition temperatures as high as T-c similar to 3.5 and similar to 4.7K, respectively. Disorder was claimed to lead to the extremely large upper critical fields (H-c2) observed in related compounds. Despite the presence of disorder and heavier elements, H-c2s in Ta4Pd3Te16 are found to be considerably smaller than those of Nb3PdxSe7 while displaying an anomalous, nonsaturating linear...
Show moreBoth Nb3PdxSe7 and Ta4Pd3Te16 crystallize in a monoclinic point group while exhibiting superconducting transition temperatures as high as T-c similar to 3.5 and similar to 4.7K, respectively. Disorder was claimed to lead to the extremely large upper critical fields (H-c2) observed in related compounds. Despite the presence of disorder and heavier elements, H-c2s in Ta4Pd3Te16 are found to be considerably smaller than those of Nb3PdxSe7 while displaying an anomalous, nonsaturating linear dependence on temperature T for fields along all three crystallographic axes. In contrast, crystals of the latter compound displaying the highest T(c)s display H-c2 alpha (1-T/T-c)(1/2), which in monolayers of transition metal dichalcogenides is claimed to be evidence for an Ising paired superconducting state resulting from strong spin-orbit coupling. This anomalous T dependence indicates that the superconducting state of Nb3PdxSe7 is quasi-two-dimensional in nature. This is further supported by a nearly divergent anisotropy in upper-critical fields, i.e., gamma= H-c2(b)/H-c2(a)', upon approaching T-c. Hence, in Nb3PdxSe7 the increase of T-c correlates with a marked reduction in electronic dimensionality as observed, for example, in intercalated FeSe. For the Nb compound, Density functional theory (DFT) calculations indicate that an increase in the external field produces an anisotropic orbital response, with especially strong polarization at the Pd sites when the field is perpendicular to their square planar environment. The field also produces an anisotropic spin moment at both Pd sites. Therefore, DFT suggests the field-induced pinning of the spin to the lattice as a possible mechanism for decoupling the superconducting planes.
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Date Issued: 2016-09-12
Identifier: FSU_libsubv1_wos_000383138700005, 10.1103/PhysRevB.94.094511
Format: Citation

Title: Jain-2/5 Parent Hamiltonian: Structure Of Zero Modes, Dominance Patterns, And Zero Mode Generators.
Creator: Chen, Li, Bandyopadhyay, Sumanta, Seidel, Alexander
Abstract/Description: We analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain-2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a four-dimensional two-particle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about ground-state uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is...
Show moreWe analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain-2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a four-dimensional two-particle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about ground-state uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is given to second-quantized methods, where zero mode properties are derived not from given analytic wave functions, but from a "lattice" Hamiltonian and associated zero mode conditions. This method reveals new insights into the guiding-center structure of the unprojected Jain-2/5 state, in particular, a system of dominance patterns following a "generalized Pauli principle," which establishes a complete one-to-one correspondence with the edge mode counting. We also identify one-body operators that function as generators of zero modes.
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Date Issued: 2017-05-31
Identifier: FSU_libsubv1_wos_000402463500001, 10.1103/PhysRevB.95.195169
Format: Citation

Title: Multistage symmetry breaking in the breathing pyrochlore lattice Li(Ga,In)Cr4O8.
Creator: Lee, S., Do, S.-H., Lee, W.-J., Choi, Y. S., Lee, M., Choi, E. S., Reyes, A. P., Kuhns, P. L., Ozarowski, A., Choi, K.-Y.
Abstract/Description: We present magnetic susceptibility, dielectric constant, high-frequency electron spin resonance, Li-7 nuclear magnetic resonance, and zero-field muon spin relaxation measurements of LiACr(4)O(8) (A = Ga, In), towards realizing a breathing pyrochlore lattice. Unlike the uniform pyrochlore ZnCr2O4 lattice, both the In and the Ga compounds feature two-stage symmetry breaking: a magnetostructural phase transition with subsequent antiferromagnetic ordering. We find a disparate symmetry breaking...
Show moreWe present magnetic susceptibility, dielectric constant, high-frequency electron spin resonance, Li-7 nuclear magnetic resonance, and zero-field muon spin relaxation measurements of LiACr(4)O(8) (A = Ga, In), towards realizing a breathing pyrochlore lattice. Unlike the uniform pyrochlore ZnCr2O4 lattice, both the In and the Ga compounds feature two-stage symmetry breaking: a magnetostructural phase transition with subsequent antiferromagnetic ordering. We find a disparate symmetry breaking process between the In and the Ga compounds, having different degrees of bond alternation. Our data reveal that the Ga compound with moderate bond alternation shows the concomitant structural and magnetic transition at T-S = 15.2 K, followed by the magnetic ordering at T-m = 12.9 K. In contrast, the In compound with strong bond alternation undergoes a thermal crossover at T* approximate to 20.1 K from a tetramer singlet to a dimer singlet or a correlated paramagnet with a separate weak magnetostructural transition at T-S = 17.6 K and the second antiferromagnetic ordering at T-m = 13.7 K. This suggests that the magnetic phases and correlations of the breathing pyrochlore lattice can be determined from the competition between bond alternation and spin-lattice coupling, thus stabilizing long-range magnetic ordering against a nonmagnetic singlet.
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Date Issued: 2016-05-02
Identifier: FSU_libsubv1_wos_000375525700002, 10.1103/PhysRevB.93.174402
Format: Citation

Title: Persistence Of Slow Fluctuations In The Overdoped Regime Of Ba(fe1-xrhx)(2)as-2 Superconductors.
Creator: Bossoni, L., Moroni, M., Julien, M. H., Mayaffre, H., Canfield, P. C., Reyes, A., Halperin, W. P., Carretta, P.
Abstract/Description: We present nuclear magnetic resonance evidence that very slow (<= 1 MHz) spin fluctuations persist into the overdoped regime of Ba(Fe1-xRhx)(2)As-2 superconductors. Measurements of the As-75 spin echo decay rate, obtained both with Hahn Echo and Carr Purcell Meiboom Gill pulse sequences, show that the slowing down of spin fluctuations can be described by short-range diffusive dynamics, likely involving domain walls motions separating (pi/a, 0) from (0, pi/a) correlated regions. This slowing...
Show moreWe present nuclear magnetic resonance evidence that very slow (<= 1 MHz) spin fluctuations persist into the overdoped regime of Ba(Fe1-xRhx)(2)As-2 superconductors. Measurements of the As-75 spin echo decay rate, obtained both with Hahn Echo and Carr Purcell Meiboom Gill pulse sequences, show that the slowing down of spin fluctuations can be described by short-range diffusive dynamics, likely involving domain walls motions separating (pi/a, 0) from (0, pi/a) correlated regions. This slowing down of the fluctuations is weakly sensitive to the external magnetic field and, although fading away with doping, it extends deeply into the overdoped regime.
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Date Issued: 2016-06-23
Identifier: FSU_libsubv1_wos_000378305600003, 10.1103/PhysRevB.93.224517
Format: Citation

Title: Peculiarities of superconductivity in the single-layer FeSe/SrTiO3 interface.
Creator: Gor'kov, Lev P.
Abstract/Description: Observation of replica bands in the angle-resolved photoemission spectroscopy (ARPES) spectra of single-layer FeSe on a strontium titanate substrate revealed a phonon component contribution to mechanisms behind its high-T-c superconductivity. We study the interaction of the in-layer FeSe electrons with the electric potential of the longitudinal (LO) modes at the surface of bulk SrTiO3. A two-dimensional system of charges at the FeSe/SrTiO3 interface includes both the itinerant and the...
Show moreObservation of replica bands in the angle-resolved photoemission spectroscopy (ARPES) spectra of single-layer FeSe on a strontium titanate substrate revealed a phonon component contribution to mechanisms behind its high-T-c superconductivity. We study the interaction of the in-layer FeSe electrons with the electric potential of the longitudinal (LO) modes at the surface of bulk SrTiO3. A two-dimensional system of charges at the FeSe/SrTiO3 interface includes both the itinerant and the immobile electrons. The latter significantly change the interface characteristics, increasing screening at the substrate surface and thereby reducing the strength of the electron-LO-phonon interaction. In what follows, the dielectric constant serves as a free parameter and is determined using the ARPES measurements of the replicas. Two-dimensional Coulomb screening is accounted for in the random-phase approximation. It is shown that the model is applicable over the entire range of the parameters typical for current experiments. The estimates from this model make possible the conclusion that the LO-phonon-mediated pairing alone cannot account for the temperatures of the superconducting transitions T-c in the single-layer FeSe/SrTiO3 reported in these experiments. This does not exclude that the LO-phonon mechanisms can become more significant in differently and better prepared single-layer FeSe films. Available experiments are briefly discussed. Thus far no measurements exist on the dependence of T-c on the concentration of electrons doped into the in-layer FeSe band.
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Date Issued: 2016-02-12
Identifier: FSU_libsubv1_wos_000370021500003, 10.1103/PhysRevB.93.060507
Format: Citation

Title: Probing 5 f -state configurations in URu2Si2 with U L-III-edge resonant x-ray emission spectroscopy.
Creator: Booth, C. H., Medling, S. A., Tobin, J. G., Baumbach, R. E., Bauer, E. D., Sokaras, D., Nordlund, D., Weng, T.-C.
Abstract/Description: Resonant x-ray emission spectroscopy (RXES) was employed at the U L-III absorption edge and the L-alpha 1 emission line to explore the 5f occupancy, n(f), and the degree of 5f -orbital delocalization in the hidden-order compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alpha-U, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with n(f) = 2.87 +/- 0.08, and does not change with temperature down to 10 K within the estimated error....
Show moreResonant x-ray emission spectroscopy (RXES) was employed at the U L-III absorption edge and the L-alpha 1 emission line to explore the 5f occupancy, n(f), and the degree of 5f -orbital delocalization in the hidden-order compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alpha-U, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with n(f) = 2.87 +/- 0.08, and does not change with temperature down to 10 K within the estimated error. These results place further constraints on theoretical explanations of the hidden order, especially those requiring a localized f(2) ground state.
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Date Issued: 2016-07-15
Identifier: FSU_libsubv1_wos_000379651600007, 10.1103/PhysRevB.94.045121
Format: Citation

Title: Possible Nematic Spin Liquid In Spin-1 Antiferromagnetic System On The Square Lattice: Implications For The Nematic Paramagnetic State Of Fese.
Creator: Gong, Shou-Shu, Zhu, W., Sheng, D. N., Yang, Kun
Abstract/Description: The exotic normal state of iron chalcogenide superconductor FeSe, which exhibits vanishing magnetic order and possesses an electronic nematic order, triggered extensive explorations of its magnetic ground state. To understand its novel properties, we study the ground state of a highly frustrated spin-1 system with bilinear-biquadratic interactions using an unbiased large-scale density matrix renormalization group. Remarkably, with increasing biquadratic interactions, we find a paramagnetic...
Show moreThe exotic normal state of iron chalcogenide superconductor FeSe, which exhibits vanishing magnetic order and possesses an electronic nematic order, triggered extensive explorations of its magnetic ground state. To understand its novel properties, we study the ground state of a highly frustrated spin-1 system with bilinear-biquadratic interactions using an unbiased large-scale density matrix renormalization group. Remarkably, with increasing biquadratic interactions, we find a paramagnetic phase between Neel and stripe magnetic ordered phases. We identify this phase as a candidate of nematic quantum spin liquid by the compelling evidences, including vanished spin and quadrupolar orders, absence of lattice translational symmetry breaking, and a persistent nonzero lattice nematic order in the thermodynamic limit. The established quantum phase diagram naturally explains the observations of enhanced spin fluctuations of FeSe in neutron scattering measurement and the phase transition with increasing pressure. This identified paramagnetic phase provides a possibility to understand the novel properties of FeSe.
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Date Issued: 2017-05-19
Identifier: FSU_libsubv1_wos_000401654300004, 10.1103/PhysRevB.95.205132
Format: Citation

Title: Revisiting The Ground State Of Coal2o4: Comparison To The Conventional Antiferromagnet Mnal2o4.
Creator: MacDougall, G. J., Aczel, A. A., Su, Yixi, Schweika, W., Faulhaber, E., Schneidewind, A., Christianson, A. D., Zarestky, J. L., Zhou, H. D., Mandrus, D., Nagler, S. E.
Abstract/Description: The A-site spinel material CoAl2O4 is a physical realization of the frustrated diamond-lattice antiferromagnet, a model in which unique incommensurate or "spin-spiral-liquid" ground states are predicted. Our previous single-crystal neutron scattering study instead classified it as a "kinetically inhibited" antiferromagnet, where the long-ranged correlations of a collinear Neel ground state are blocked by the freezing of domain-wall motion below a first-order phase transition at T* = 6.5 K....
Show moreThe A-site spinel material CoAl2O4 is a physical realization of the frustrated diamond-lattice antiferromagnet, a model in which unique incommensurate or "spin-spiral-liquid" ground states are predicted. Our previous single-crystal neutron scattering study instead classified it as a "kinetically inhibited" antiferromagnet, where the long-ranged correlations of a collinear Neel ground state are blocked by the freezing of domain-wall motion below a first-order phase transition at T* = 6.5 K. This paper provides new data sets from a number of experiments, which support and expand this work in several important ways. We show that the phenomenology leading to the kinetically inhibited order is unaffected by sample measured and instrument resolution, while new low-temperature measurements reveal spin correlations are unchanging between T = 2 K and 250 mK, consistent with a frozen state. Polarized diffuse neutron measurements show several interesting magnetic features, which can be entirely explained by the existence of short-ranged Neel order. Finally, and crucially, this paper presents some neutron scattering studies of single crystalline MnAl2O4, which acts as an unfrustrated analog to CoAl2O4 and shows all the hallmarks of a classical antiferromagnet with a continuous phase transition to Neel order at T-N = 39 K. Direct comparison between the two compounds indicates that CoAl2O4 is unique, not in the nature of high-temperature diffuse correlations, but rather in the nature of the frozen state below T*. The higher level of cation inversion in the MnAl2O4 sample indicates that this behavior is primarily an effect of greater next-nearest-neighbor exchange.
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Date Issued: 2016-11-17
Identifier: FSU_libsubv1_wos_000387887100005, 10.1103/PhysRevB.94.184422
Format: Citation

Title: Quantum Oscillation Studies Of The Topological Semimetal Candidate Zrgem (m = S, Se, Te).
Creator: Hu, J., Zhu, Y. L., Graf, D., Tang, Z. J., Liu, J. Y., Mao, Z. Q.
Abstract/Description: The WHM-type materials (W = Zr/Hf/La, H = Si/Ge/Sn/Sb, M = O/S/Se/Te) have been predicted to be a large pool of topological materials. These materials allow for fine tuning of spin-orbit coupling, lattice constant, and structural dimensionality for various combinations of W, H, and M elements, thus providing an excellent platform to study how these parameters' tuning affects topological semimetal state. In this paper, we report high field quantum oscillation studies on ZrGeM (M = S, Se, and...
Show moreThe WHM-type materials (W = Zr/Hf/La, H = Si/Ge/Sn/Sb, M = O/S/Se/Te) have been predicted to be a large pool of topological materials. These materials allow for fine tuning of spin-orbit coupling, lattice constant, and structural dimensionality for various combinations of W, H, and M elements, thus providing an excellent platform to study how these parameters' tuning affects topological semimetal state. In this paper, we report high field quantum oscillation studies on ZrGeM (M = S, Se, and Te), from which we have revealed properties consistent with the theoretically predicted topological semimetal states. From the angular dependence of quantum oscillation frequency, we have also studied the Fermi surface topologies of these materials. Moreover, we have compared Dirac electron behavior between the ZrGeM and ZrSiM systems, which reveals deep insights to the tuning of Dirac state by spin-orbit coupling and lattice constants in the WHM system.
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Date Issued: 2017-05-22
Identifier: FSU_libsubv1_wos_000402003700006, 10.1103/PhysRevB.95.205134
Format: Citation

Title: Quantum antiferromagnetic Heisenberg half-odd-integer spin model as the entanglement Hamiltonian of the integer-spin Affleck-Kennedy-Lieb-Tasaki states.
Creator: Rao, Wen-Jia, Zhang, Guang-Ming, Yang, Kun
Abstract/Description: Applying a symmetric bulk bipartition to the one-dimensional Affleck-Kennedy-Lieb-Tasaki valence-bond solid (VBS) states for the integer spin-S Haldane gapped phase, we can create an array of fractionalized spin-S/2 edge states with the super unit cell l in the reduced bulk system, and the topological properties encoded in the VBS wave functions can be revealed. The entanglement Hamiltonian (EH) with even l corresponds to the quantum antiferromagnetic Heisenberg spin-S/2 model. For the even...
Show moreApplying a symmetric bulk bipartition to the one-dimensional Affleck-Kennedy-Lieb-Tasaki valence-bond solid (VBS) states for the integer spin-S Haldane gapped phase, we can create an array of fractionalized spin-S/2 edge states with the super unit cell l in the reduced bulk system, and the topological properties encoded in the VBS wave functions can be revealed. The entanglement Hamiltonian (EH) with even l corresponds to the quantum antiferromagnetic Heisenberg spin-S/2 model. For the even integer spins, the EH still describes the Haldane gapped phase. For the odd integer spins, however, the EH just corresponds to the quantum antiferromagnetic Heisenberg half-odd integer-spin model with spinon excitations, characterizing the critical point separating the topological Haldane phase from the trivial gapped phase. Our results thus demonstrate that the topological bulk property not only determines its fractionalized edge states but also the quantum criticality associated with the topological phase, where the elementary excitations are precisely those fractionalized edge degrees of freedom confined in the bulk of the topological phase.
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Date Issued: 2016-03-15
Identifier: FSU_libsubv1_wos_000372409100002, 10.1103/PhysRevB.93.115125
Format: Citation

Title: Probing critical surfaces in momentum space using real-space entanglement entropy: Bose versus Fermi.
Creator: Lai, Hsin-Hua, Yang, Kun
Abstract/Description: A codimension-one critical surface in momentum space can be either a familiar Fermi surface, which separates occupied states from empty ones in the noninteracting fermion case, or a novel Bose surface, where gapless bosonic excitations are anchored. The presence of such surfaces gives rise to logarithmic violation of entanglement entropy area law. When they are convex, we show that the shape of these critical surfaces can be determined by inspecting the leading logarithmic term of real-space...
Show moreA codimension-one critical surface in momentum space can be either a familiar Fermi surface, which separates occupied states from empty ones in the noninteracting fermion case, or a novel Bose surface, where gapless bosonic excitations are anchored. The presence of such surfaces gives rise to logarithmic violation of entanglement entropy area law. When they are convex, we show that the shape of these critical surfaces can be determined by inspecting the leading logarithmic term of real-space entanglement entropy. The fundamental difference between a Fermi surface and a Bose surface is revealed by the fact that the logarithmic terms in entanglement entropies differ by a factor of 2: S-log(Bose) = 2S(log)(Fermi), even when they have identical geometry. Our method has remarkable similarity with determining Fermi surface shape using quantum oscillation. We also discuss possible probes of concave critical surfaces in momentum space.
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Date Issued: 2016-03-23
Identifier: FSU_libsubv1_wos_000372716500001, 10.1103/PhysRevB.93.121109
Format: Citation

Title: Spin correlations and topological entanglement entropy in a non-Abelian spin-one spin liquid.
Creator: Wildeboer, Julia, Bonesteel, N. E.
Abstract/Description: We analyze the properties of a non-Abelian spin-one chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 Moore-Read Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a three-dimensional space of these states corresponding to the topological degeneracy of the bosonic Moore-Read state on the...
Show moreWe analyze the properties of a non-Abelian spin-one chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 Moore-Read Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a three-dimensional space of these states corresponding to the topological degeneracy of the bosonic Moore-Read state on the torus. We show that spin correlations for different states in this space become indistinguishable for large system size. We also calculate the Renyi entanglement entropy for different system partitions to extract the topological entanglement entropy and provide evidence that the topological order of the lattice spin-liquid state is the same as that of the continuum Moore-Read state from which it is constructed.
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Date Issued: 2016-07-18
Identifier: FSU_libsubv1_wos_000380104300008, 10.1103/PhysRevB.94.045125
Format: Citation

Title: Charge avalanches and depinning in the Coulomb glass: The role of long-range interactions.
Creator: Andresen, Juan Carlos, Pramudya, Yohanes, Katzgraber, Helmut G., Thomas, Creighton K., Zimanyi, Gergely T., Dobrosavljevic, V.
Abstract/Description: We explore the stability of far-from-equilibrium metastable states of a three-dimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particle-conserving dynamics, scale-free system-spanning avalanches are observed only at the...
Show moreWe explore the stability of far-from-equilibrium metastable states of a three-dimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particle-conserving dynamics, scale-free system-spanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent short-range model, highlighting the key importance of long-range interactions for nonequilibrium dynamics of Coulomb glasses.
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Date Issued: 2016-03-24
Identifier: FSU_libsubv1_wos_000372712000002, 10.1103/PhysRevB.93.094429
Format: Citation

Title: Chiral spin liquid from magnetic Wannier states.
Creator: Panfilov, I., Patri, A., Yang, Kun, Burkov, A. A.
Abstract/Description: We present a mapping of a two-dimensional system of interacting bosons in a strong perpendicular magnetic field to an equivalent system of interacting bosons on the square lattice in the absence of the field. The mapping utilizes a magnetic Bloch and the corresponding magnetic Wannier single-particle basis in the lowest Landau level. By construction, the ground states of the resulting model of interacting bosons on the square lattice are gapped fractionalized liquids or gapless Bose metal...
Show moreWe present a mapping of a two-dimensional system of interacting bosons in a strong perpendicular magnetic field to an equivalent system of interacting bosons on the square lattice in the absence of the field. The mapping utilizes a magnetic Bloch and the corresponding magnetic Wannier single-particle basis in the lowest Landau level. By construction, the ground states of the resulting model of interacting bosons on the square lattice are gapped fractionalized liquids or gapless Bose metal states with broken time-reversal symmetry at specific rational filling fractions.
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Date Issued: 2016-03-16
Identifier: FSU_libsubv1_wos_000372413000006, 10.1103/PhysRevB.93.125126
Format: Citation

Title: Changes in the electronic structure and spin dynamics across the metal-insulator transition in La1-xSrxCoO3.
Creator: Smith, R. X., Hoch, M. J. R., Moulton, W. G., Kuhns, P. L., Reyes, A. P., Boebinger, G. S., Zheng, H., Mitchell, J. F.
Abstract/Description: The magnetoelectronic properties of La1-xSrxCoO3, which include giant magnetoresistance, are strongly dependent on the level of hole doping. The system evolves, with increasing x, from a spin glass insulator to a metallic ferromagnet with a metal-insulator (MI) transition at x(C) similar to 0.18. Nanoscale phase separation occurs in the insulating phase and persists, to some extent, into the just-metallic phase. The present experiments at 4.2 K have used La-139 nuclear magnetic resonance to...
Show moreThe magnetoelectronic properties of La1-xSrxCoO3, which include giant magnetoresistance, are strongly dependent on the level of hole doping. The system evolves, with increasing x, from a spin glass insulator to a metallic ferromagnet with a metal-insulator (MI) transition at x(C) similar to 0.18. Nanoscale phase separation occurs in the insulating phase and persists, to some extent, into the just-metallic phase. The present experiments at 4.2 K have used La-139 nuclear magnetic resonance to investigate the transition from hopping dynamics for x < x(C) to Korringa-like ferromagnetic metal behavior for x > x(C). A marked decrease in the spin-lattice relaxation rate is found in the vicinity of x(C) as the MI transition is crossed. This behavior is accounted for in terms of the evolution of the electronic structure and dynamics with cluster size.
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Date Issued: 2016-01-25
Identifier: FSU_libsubv1_wos_000369218500003, 10.1103/PhysRevB.93.024204
Format: Citation

Title: Incommensurate crystal supercell and polarization flop observed in the magnetoelectric ilmenite MnTiO3.
Creator: Silverstein, Harlyn J., Skoropata, Elizabeth, Sarte, Paul M., Mauws, Cole, Aczel, Adam A., Choi, Eun Sang, van Lierop, Johan, Wiebe, Christopher R., Zhou, Haidong
Abstract/Description: MnTiO3 has been studied for many decades, but it was only in the last few years that its magnetoelectric behavior had been observed. Here, we use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R ...
Show moreMnTiO3 has been studied for many decades, but it was only in the last few years that its magnetoelectric behavior had been observed. Here, we use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R (3) over bar symmetry) followed by a polarization flop accompanying the spin flop transition at mu H-0(SF) = 6.5T. Mossbauer spectroscopy on MnTiO3 gently doped with Fe-57 was used to help shed light on the impact of the supercell on the observed behavior. Although the full supercell structure could not be solved at this time due to a lack of visible reflections, the full scope of the results presented here suggest that the role of local spin-lattice coupling in the magnetoelectric properties of MnTiO3 is likely more important than previously thought.
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Date Issued: 2016-02-19
Identifier: FSU_libsubv1_wos_000370485900001, 10.1103/PhysRevB.93.054416
Format: Citation

Title: Interlayer Electronic Transport In Camnbi2 Antiferromagnet.
Creator: Wang, Aifeng, Graf, D., Wu, Lijun, Wang, Kefeng, Bozin, E., Zhu, Yimei, Petrovic, C.
Abstract/Description: We report interlayer electronic transport in CaMnBi2 single crystals. Quantum oscillations and angular magnetoresistance suggest coherent electronic conduction and valley polarized conduction of Dirac states. The small cyclotron mass, high mobility of carriers, and nontrivial Berry's phase are consistent with the presence of Dirac fermions on the side wall of the warped cylindrical Fermi surface. Similarly to SrMnBi2, which features an anisotropic Dirac cone, our results suggest that magnetic...
Show moreWe report interlayer electronic transport in CaMnBi2 single crystals. Quantum oscillations and angular magnetoresistance suggest coherent electronic conduction and valley polarized conduction of Dirac states. The small cyclotron mass, high mobility of carriers, and nontrivial Berry's phase are consistent with the presence of Dirac fermions on the side wall of the warped cylindrical Fermi surface. Similarly to SrMnBi2, which features an anisotropic Dirac cone, our results suggest that magnetic-field-induced changes in interlayer conduction are also present in layered bismuth-based materials with a zero-energy line in momentum space created by the staggered alkaline earth atoms.
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Date Issued: 2016-09-12
Identifier: FSU_libsubv1_wos_000383145300004, 10.1103/PhysRevB.94.125118
Format: Citation

$Interaction-driven fractional quantum Hall state of hard-core bosons on kagome lattice at one-third filling$

Title: Interaction-driven Fractional Quantum Hall State Of Hard-core Bosons On Kagome Lattice At One-third Filling.
Creator: Zhu, W., Gong, S. S., Sheng, D. N.
Abstract/Description: There has been a growing interest in realizing topologically nontrivial states of matter in band insulators, where a quantum Hall effect can appear as an intrinsic property of the band structure. While ongoing progress is under way with a number of directions, the possibility of realizing novel interaction-generated topological phases, without the requirement of a nontrivial invariant encoded in single-particle wave function or band structure, can significantly extend the class of topological...
Show moreThere has been a growing interest in realizing topologically nontrivial states of matter in band insulators, where a quantum Hall effect can appear as an intrinsic property of the band structure. While ongoing progress is under way with a number of directions, the possibility of realizing novel interaction-generated topological phases, without the requirement of a nontrivial invariant encoded in single-particle wave function or band structure, can significantly extend the class of topological materials and is thus of great importance. Here, we show an interaction-driven topological phase emerging in an extended Bose-Hubbard model on a kagome lattice, where the noninteracting band structure is topological trivial with zero Berry curvature in the Brillouin zone. By means of an unbiased state-of-the-art density-matrix renormalization group technique, we identify that the ground state in a broad parameter region is equivalent to a bosonic fractional quantum Hall Laughlin state, based on the characterization of universal properties including ground-state degeneracy, edge excitations, and anyonic quasiparticle statistics. Our work paves a way to finding an interaction-induced topological phase at the phase boundary of conventionally ordered solid phases.
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Date Issued: 2016-07-13
Identifier: FSU_libsubv1_wos_000379502800001, 10.1103/PhysRevB.94.035129
Format: Citation

Title: Cyclotron decay time of a two-dimensional electron gas from 0.4 to 100 K.
Creator: Curtis, Jeremy A., Tokumoto, Takahisa, Hatke, A. T., Cherian, Judy G., Reno, John L., McGill, Stephen A., Karaiskaj, Denis, Hilton, David J.
Abstract/Description: We have studied the cyclotron decay time of a Landau-quantized two-dimensional electron gas as a function of temperature (0.4-100 K) at a fixed magnetic field (+/- 1.25 T) using terahertz time-domain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V-1 s(-1) and a carrier concentration of n(s) = 2 x 10(11) cm(-2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may...
Show moreWe have studied the cyclotron decay time of a Landau-quantized two-dimensional electron gas as a function of temperature (0.4-100 K) at a fixed magnetic field (+/- 1.25 T) using terahertz time-domain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V-1 s(-1) and a carrier concentration of n(s) = 2 x 10(11) cm(-2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may result from both dissipative processes as well as a decrease in n(s) below 1.5K. Shubnikov-de Haas characterization determines a quantum lifetime, tau(q) = 1.1 ps, which is significantly faster than the corresponding dephasing time, tau(s) = 66.4 ps, in our cyclotron data. This is consistent with small-angle scattering as the dominant contribution in this sample, where scattering angles below theta <= 13 degrees. do not efficiently contribute to dephasing. Above 50 K, the cyclotron oscillations show a strong reduction in both the oscillation amplitude and lifetime that result from polar optical phonon scattering.
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Date Issued: 2016-04-29
Identifier: FSU_libsubv1_wos_000375202600004, 10.1103/PhysRevB.93.155437
Format: Citation

Title: Effective two-dimensional thickness for the Berezinskii-Kosterlitz-Thouless-like transition in a highly underdoped La2-xSrxCuO4.
Creator: Baity, P. G., Shi, Xiaoyan, Shi, Zhenzhong, Benfatto, L., Popovic, Dragana
Abstract/Description: The nature of the superconducting transition in highly underdoped thick films of La2-xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the in-plane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear...
Show moreThe nature of the superconducting transition in highly underdoped thick films of La2-xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the in-plane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear current-voltage (I - V) characteristics measured across it exhibit the main signatures of the Berezinskii-Kosterlitz-Thouless (BKT) transition. The quantitative comparison of the superfluid stiffness, extracted from the I - V data, with the renormalization-group results for the BKT theory, reveals a large value of the vortex-core energy. This finding is confirmed by the analysis of the paraconductivity obtained using different methods. The results strongly suggest that the characteristic energy scale controlling the BKT behavior in this layered system corresponds to the superfluid stiffness of a few layers.
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Date Issued: 2016-01-25
Identifier: FSU_libsubv1_wos_000369218500009, 10.1103/PhysRevB.93.024519
Format: Citation

Title: Electrical Transport Properties Of Single-crystal Cab6, Srb6, And Bab6.
Creator: Stankiewicz, Jolanta, Rosa, Priscila F. S., Schlottmann, Pedro, Fisk, Zachary
Abstract/Description: The electrical resistivity and Hall effect of alkaline-earth-metal hexaboride single crystals are measured as a function of temperature, hydrostatic pressure, and magnetic field. The transport properties vary weakly with the external parameters and are modeled in terms of intrinsic variable-valence defects. These defects can stay either in (1) delocalized shallow levels or in (2) localized levels resonant with the conduction band, which can be neutral or negatively charged. Satisfactory...
Show moreThe electrical resistivity and Hall effect of alkaline-earth-metal hexaboride single crystals are measured as a function of temperature, hydrostatic pressure, and magnetic field. The transport properties vary weakly with the external parameters and are modeled in terms of intrinsic variable-valence defects. These defects can stay either in (1) delocalized shallow levels or in (2) localized levels resonant with the conduction band, which can be neutral or negatively charged. Satisfactory agreement is obtained for electronic transport properties in a broad temperature and pressure range, although fitting the magnetoresistance is less straightforward and a combination of various mechanisms is needed to explain the field and temperature dependences.
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Date Issued: 2016-09-22
Identifier: FSU_libsubv1_wos_000383865700005, 10.1103/PhysRevB.94.125141
Format: Citation

Title: Gutzwiller renormalization group.
Creator: Lanata, Nicola, Yao, Yong-Xin, Deng, Xiaoyu, Wang, Cai-Zhuang, Ho, Kai-Ming, Kotliar, Gabriel
Abstract/Description: We develop a variational scheme called the "Gutzwiller renormalization group" (GRG), which enables us to calculate the ground state of Anderson impurity models (AIM) with arbitrary numerical precision. Our method exploits the low-entanglement property of the ground state of local Hamiltonians in combination with the framework of the Gutzwiller wave function and indicates that the ground state of the AIM has a very simple structure, which can be represented very accurately in terms of a...
Show moreWe develop a variational scheme called the "Gutzwiller renormalization group" (GRG), which enables us to calculate the ground state of Anderson impurity models (AIM) with arbitrary numerical precision. Our method exploits the low-entanglement property of the ground state of local Hamiltonians in combination with the framework of the Gutzwiller wave function and indicates that the ground state of the AIM has a very simple structure, which can be represented very accurately in terms of a surprisingly small number of variational parameters. We perform benchmark calculations of the single-band AIM that validate our theory and suggest that the GRG might enable us to study complex systems beyond the reach of the other methods presently available and pave the way to interesting generalizations, e.g., to nonequilibrium transport in nanostructures.
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Date Issued: 2016-01-06
Identifier: FSU_libsubv1_wos_000367665400002, 10.1103/PhysRevB.93.045103
Format: Citation

Title: Determination Of The Effective Kinematic Viscosity For The Decay Of Quasiclassical Turbulence In Superfluid He-4.
Creator: Gao, J., Guo, W., Vinen, W. F.
Abstract/Description: The energy dissipation of quasiclassical homogeneous turbulence in superfluid He-4 (He II) is controlled by an effective kinematic viscosity nu', which relates the energy decay rate dE / dt to the density of quantized vortex lines L as dE / dt = -nu'(kappa L)(2). The precise value of nu' is of fundamental importance in developing our understanding of the dissipation mechanism in He II, and it is also needed in many high-Reynolds-number turbulence experiments and model testing that use He II...
Show moreThe energy dissipation of quasiclassical homogeneous turbulence in superfluid He-4 (He II) is controlled by an effective kinematic viscosity nu', which relates the energy decay rate dE / dt to the density of quantized vortex lines L as dE / dt = -nu'(kappa L)(2). The precise value of nu' is of fundamental importance in developing our understanding of the dissipation mechanism in He II, and it is also needed in many high-Reynolds-number turbulence experiments and model testing that use He II as the working fluid. However, a reliable determination of nu' requires the measurements of both E(t) and L(t), which was never achieved. Here we discuss our study of the quasiclassical turbulence that emerges in the decay of thermal counterflow in He II above 1 K. We were able to measure E(t) by using a recently developed flow-visualization technique and L(t) via second-sound attenuation. We report the nu' values in a wide temperature range determined from a comparison of the time evolution of E(t) and L(t).
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Date Issued: 2016-09-01
Identifier: FSU_libsubv1_wos_000383033500004, 10.1103/PhysRevB.94.094502
Format: Citation

Title: Emergent Quasi-one-dimensionality In A Kagome Magnet: A Simple Route To Complexity.
Creator: Gong, Shou-Shu, Zhu, Wei, Yang, Kun, Starykh, Oleg A., Sheng, D. N., Balents, Leon
Abstract/Description: We study the ground-state phase diagram of the quantum spin-1/2 Heisenberg model on the kagome lattice with first-(J(1) < 0), second-(J(2) < 0), and third-neighbor interactions (J(d) > 0) by means of analytical low-energy field theory and numerical density-matrix renormalization group (DMRG) studies. The results offer a consistent picture of the J(d)-dominant regime in terms of three sets of spin chains weakly coupled by the ferromagnetic interchain interactions J(1,2). When either J(1) or J...
Show moreWe study the ground-state phase diagram of the quantum spin-1/2 Heisenberg model on the kagome lattice with first-(J(1) < 0), second-(J(2) < 0), and third-neighbor interactions (J(d) > 0) by means of analytical low-energy field theory and numerical density-matrix renormalization group (DMRG) studies. The results offer a consistent picture of the J(d)-dominant regime in terms of three sets of spin chains weakly coupled by the ferromagnetic interchain interactions J(1,2). When either J(1) or J(2) is much stronger than the other one, the model is found to support one of two cuboctohedral phases, cuboc1, and cuboc2. These cuboc states host noncoplanar long-ranged magnetic order and possess finite scalar spin chirality. However, in the compensated regime J(1) similar or equal to J(2), a valence bond crystal phase emerges between the two cuboc phases. We find excellent agreement between an analytical theory based on coupled spin chains and unbiased DMRG calculations, including at a very detailed level of comparison of the structure of the valence bond crystal state. To our knowledge, this is the first such comprehensive understanding of a highly frustrated two-dimensional quantum antiferromagnet. We find no evidence of either the one-dimensional gapless spin liquid or the chiral spin liquids, which were previously suggested by parton mean-field theories.
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Date Issued: 2016-07-27
Identifier: FSU_libsubv1_wos_000381482700001, 10.1103/PhysRevB.94.035154
Format: Citation

Title: Electron-hole asymmetry, Dirac fermions, and quantum magnetoresistance in BaMnBi2.
Creator: Li, Lijun, Wang, Kefeng, Graf, D., Wang, Limin, Wang, Aifeng, Petrovic, C.
Abstract/Description: We report two-dimensional quantum transport and Dirac fermions in BaMnBi2 single crystals. BaMnBi2 is a layered bad metal with highly anisotropic conductivity and magnetic order below 290 K. Magnetotransport properties, nonzero Berry phase, small cyclotronmass, and the first-principles band structure calculations indicate the presence of Dirac fermions in Bi square nets. Quantum oscillations in the Hall channel suggest the presence of both electron and hole pockets, whereas Dirac and...
Show moreWe report two-dimensional quantum transport and Dirac fermions in BaMnBi2 single crystals. BaMnBi2 is a layered bad metal with highly anisotropic conductivity and magnetic order below 290 K. Magnetotransport properties, nonzero Berry phase, small cyclotronmass, and the first-principles band structure calculations indicate the presence of Dirac fermions in Bi square nets. Quantum oscillations in the Hall channel suggest the presence of both electron and hole pockets, whereas Dirac and parabolic states coexist at the Fermi level.
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Date Issued: 2016-03-28
Identifier: FSU_libsubv1_wos_000372799100001, 10.1103/PhysRevB.93.115141
Format: Citation

Title: Evidence For Impact Ionization In Vanadium Dioxide.
Creator: Holleman, Joshua, Bishop, Michael M., Garcia, Carlos, Winfred, J. S. R. Vellore, Lee, Shinbuhm, Lee, Ho Nyung, Beekman, Christianne, Manousakis, Efstratios, McGill, Stephen A.
Abstract/Description: Pump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M-1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and...
Show morePump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M-1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that a fast carrier multiplication process, i.e., impact ionization, acts efficiently in this prototypical strongly correlated insulator, as was recently predicted by theoretical calculations.
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Date Issued: 2016-10-17
Identifier: FSU_libsubv1_wos_000386097100004, 10.1103/PhysRevB.94.155129
Format: Citation

Title: Crystal Structure And Partial Ising-like Magnetic Ordering Of Orthorhombic Dy2tio5.
Creator: Shamblin, Jacob, Calder, Stuart, Dun, Zhiling, Lee, Minseong, Choi, Eun Sang, Neuefeind, Joerg, Zhou, Haidong, Lang, Maik
Abstract/Description: The structure andmagnetic properties of orthorhombic Dy2TiO5 have been investigated using x-ray diffraction, neutron diffraction, and alternating current (ac)/direct current (dc) magnetic susceptibility measurements. We report a continuous structural distortion below 100 K characterized by negative thermal expansion in the [0 1 0] direction. Neutron diffraction and magnetic susceptibility measurements revealed that two-dimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a...
Show moreThe structure andmagnetic properties of orthorhombic Dy2TiO5 have been investigated using x-ray diffraction, neutron diffraction, and alternating current (ac)/direct current (dc) magnetic susceptibility measurements. We report a continuous structural distortion below 100 K characterized by negative thermal expansion in the [0 1 0] direction. Neutron diffraction and magnetic susceptibility measurements revealed that two-dimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a three-dimensional magnetic transition at 1.7 K. The magnetic structure has been solved through a representational analysis approach and can be indexed with the propagation vector k = [0 1/2 0]. The spin structure corresponds to a coplanar model of interwoven 2D "sheets" extending in the [0 1 0] direction. The local crystal field is different for each Dy3+ ion (Dy1 and Dy2), one of which possesses strong uniaxial symmetry indicative of Ising-like magnetic ordering. Consequently, two succeeding transitions under magnetic field are observed in the ac susceptibility, which are associated with flipping each Dy3+ spin independently.
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Date Issued: 2016-07-12
Identifier: FSU_libsubv1_wos_000379500900004, 10.1103/PhysRevB.94.024413
Format: Citation

Title: Electron spin resonance in a two-dimensional Fermi liquid with spin-orbit coupling.
Creator: Maiti, Saurabh, Imran, Muhammad, Maslov, Dmitrii L.
Abstract/Description: Electron spin resonance (ESR) is usually viewed as a single-particle phenomenon protected from the effect of many-body correlations. We show that this is not the case in a two-dimensional Fermi liquid (FL) with spin-orbit coupling (SOC). Depending on whether the in-plane magnetic field is below or above some critical value, ESR in such a system probes up to three chiral-spin collective modes, augmented by the spin mode in the presence of the field, or the Silin-Leggett mode. All the modes are...
Show moreElectron spin resonance (ESR) is usually viewed as a single-particle phenomenon protected from the effect of many-body correlations. We show that this is not the case in a two-dimensional Fermi liquid (FL) with spin-orbit coupling (SOC). Depending on whether the in-plane magnetic field is below or above some critical value, ESR in such a system probes up to three chiral-spin collective modes, augmented by the spin mode in the presence of the field, or the Silin-Leggett mode. All the modes are affected by both SOC and FL renormalizations. We argue that ESR can be used as a probe not only for SOC but also for many-body physics.
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Date Issued: 2016-01-26
Identifier: FSU_libsubv1_wos_000369223400008, 10.1103/PhysRevB.93.045134
Format: Citation

Title: Fermi surface reconstruction in FeSe under high pressure.
Creator: Terashima, Taichi, Kikugawa, Naoki, Kiswandhi, Andhika, Graf, David, Choi, Eun-Sang, Brooks, James S., Kasahara, Shigeru, Watashige, Tatsuya, Matsuda, Yuji, Shibauchi, Takasada,...
Show moreTerashima, Taichi, Kikugawa, Naoki, Kiswandhi, Andhika, Graf, David, Choi, Eun-Sang, Brooks, James S., Kasahara, Shigeru, Watashige, Tatsuya, Matsuda, Yuji, Shibauchi, Takasada, Wolf, Thomas, Boehmer, Anna E., Hardy, Frederic, Meingast, Christoph, Loehneysen, Hilbert V., Uji, Shinya
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Abstract/Description: We report Shubnikov-de Haas (SdH) oscillation measurements on FeSe under high pressure up to P = 16.1 kbar. We find a sudden change in SdH oscillations at the onset of the pressure-induced antiferromagnetism at P similar to 8 kbar. We argue that this change can be attributed to a reconstruction of the Fermi surface by the antiferromagnetic order. The negative dT(c)/dP observed in a range between P similar to 8 and 12 kbar may be explained by the reduction in the density of states due to the...
Show moreWe report Shubnikov-de Haas (SdH) oscillation measurements on FeSe under high pressure up to P = 16.1 kbar. We find a sudden change in SdH oscillations at the onset of the pressure-induced antiferromagnetism at P similar to 8 kbar. We argue that this change can be attributed to a reconstruction of the Fermi surface by the antiferromagnetic order. The negative dT(c)/dP observed in a range between P similar to 8 and 12 kbar may be explained by the reduction in the density of states due to the reconstruction. The ratio of the transition temperature to the effective Fermi energy remains high under high pressure: k(B)T(c)/E-F similar to 0.1 even at P = 16.1 kbar.
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Date Issued: 2016-03-03
Identifier: FSU_libsubv1_wos_000371401700003, 10.1103/PhysRevB.93.094505
Format: Citation

Title: Coulomb-interaction Induced Coupling Of Landau Levels In Intrinsic And Modulation-doped Quantum Wells.
Creator: Paul, J., Stevens, C. E., Zhang, H., Dey, P., McGinty, D., McGill, S. A., Smith, R. P., Reno, J. L., Turkowski, V., Perakis, I. E., Hilton, D. J., Karaiskaj, D.
Abstract/Description: We have performed two- dimensional Fourier transform spectroscopy on intrinsic and modulation doped quantum wells in external magnetic fields up to 10 T. In the undoped sample, the strong Coulomb interactions and the increasing separations of the electron and hole charge distributions with increasing magnetic fields lead to a nontrivial in-plane dispersion of the magneto-excitons. Thus, the discrete and degenerate Landau levels are coupled to a continuum. The signature of this continuum is...
Show moreWe have performed two- dimensional Fourier transform spectroscopy on intrinsic and modulation doped quantum wells in external magnetic fields up to 10 T. In the undoped sample, the strong Coulomb interactions and the increasing separations of the electron and hole charge distributions with increasing magnetic fields lead to a nontrivial in-plane dispersion of the magneto-excitons. Thus, the discrete and degenerate Landau levels are coupled to a continuum. The signature of this continuum is the emergence of elongated spectral line shapes at the Landau level energies, which are exposed by the multidimensional nature of our technique. Surprisingly, the elongation of the peaks is completely absent in the lowest Landau level spectra obtained from the modulation doped quantum well at high fields.
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Date Issued: 2017-06-28
Identifier: FSU_libsubv1_wos_000404469700004, 10.1103/PhysRevB.95.245314
Format: Citation

Title: Evidence For Correlated Dynamics Near The Berezinskii-kosterlitz-thouless-like Transition In Highly Underdoped La2-xsrxcuo4.
Creator: Shi, Zhenzhong, Shi, Xiaoyan, Popovic, Dragana
Abstract/Description: A low-frequency resistance noise study in highly underdoped thick films of La2-xSrxCuO4 (x = 0.07 and 0.08) reveals slow, correlated dynamics and breaking of ergodicity near the superconducting transition of the Berezinskii-Kosterlitz-Thouless type. The observed correlated behavior is strongly suppressed by disorder.
Date Issued: 2016-10-05
Identifier: FSU_libsubv1_wos_000385239900002, 10.1103/PhysRevB.94.134503
Format: Citation

Title: Extremely Large Nonsaturating Magnetoresistance And Ultrahigh Mobility Due To Topological Surface States In The Metallic Bi2te3 Topological Insulator.
Creator: Shrestha, K., Chou, M., Graf, D., Yang, H. D., Lorenz, B., Chu, C. W.
Abstract/Description: Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to...
Show moreWeak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large nonsaturating magnetoresistance and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-LarkinNagaoka formula. At high charge-carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge-carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magnetoelectric sensors and memory devices.
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Date Issued: 2017-05-08
Identifier: FSU_libsubv1_wos_000401229000004, 10.1103/PhysRevB.95.195113
Format: Citation

National High Magnetic Field Laboratory (55)	+ -
Department of Physics (35)	+ -
Department of Chemical and Biomedical Engineering (3)	+ -
Department of Chemistry and Biochemistry (2)	+ -

text (69)	+ -
journal article (19)	+ -

Yang, Kun (9)	+ -
Graf, D. (7)	+ -
Zhou, H. D. (7)	+ -
Baumbach, R. E. (6)	+ -
Balicas, L. (5)	+ -

Besara, T. (4)	+ -
Kuhns, P. L. (4)	+ -
Lee, M. (4)	+ -
Reyes, A. P. (4)	+ -
Sheng, D. N. (4)	+ -
Bauer, E. D. (3)	+ -
Chen, K.-W. (3)	+ -
Choi, E. S. (3)	+ -
Gong, Shou-Shu (3)	+ -
McGill, Stephen A. (3)	+ -
Siegrist, T. (3)	+ -
Smirnov, D. (3)	+ -
Zhang, Q. R. (3)	+ -
Zheng, H. (3)	+ -
Aczel, A. A. (2)	+ -
Cao, G. (2)	+ -
Chen, K. W. (2)	+ -
Choi, Eun Sang (2)	+ -
Dobrosavljevic, V. (2)	+ -
Du, Haifeng (2)	+ -
Dun, Z. L. (2)	+ -
Gor'kov, Lev P. (2)	+ -
Graf, David (2)	+ -
Hoch, M. J. R. (2)	+ -
Jiang, Z. (2)	+ -

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