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Title: Physical properties of the Ce2MAl7Ge4 heavy-fermion compounds (M = Co, Ir, Ni, Pd).
Creator: Ghimire, N. J., Cary, S. K., Eley, S., Wakeham, N. A., Rosa, P. F. S., Albrecht-Schmitt, T., Lee, Y., Janoschek, M., Brown, C. M., Civale, L., Thompson, J. D., Ronning, F.,...
Show moreGhimire, N. J., Cary, S. K., Eley, S., Wakeham, N. A., Rosa, P. F. S., Albrecht-Schmitt, T., Lee, Y., Janoschek, M., Brown, C. M., Civale, L., Thompson, J. D., Ronning, F., Bauer, E. D.
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Abstract/Description: We report the synthesis, crystal structure, and characterization by means of single-crystal x-ray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavy-fermion compounds Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd). These compounds crystallize in a noncentrosymmetric tetragonal space group P (4) over bar2(1)m, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. Ce2CoAl7Ge4, Ce2IrAl7Ge4, and Ce2NiAl7Ge4 order...
Show moreWe report the synthesis, crystal structure, and characterization by means of single-crystal x-ray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavy-fermion compounds Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd). These compounds crystallize in a noncentrosymmetric tetragonal space group P (4) over bar2(1)m, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. Ce2CoAl7Ge4, Ce2IrAl7Ge4, and Ce2NiAl7Ge4 order magnetically below T-M = 1.8, 1.6, and 0.8 K, respectively. There is no evidence of magnetic ordering in Ce2PdAl7Ge4 down to 0.4 K. The small amount of entropy released in the magnetic state of Ce2MAl7Ge4 (M = Co, Ir, Ni) and the reduced specific heat jump at TM suggest a strong Kondo interaction in these materials. Ce2PdAl7Ge4 shows non-Fermi liquid behavior, possibly due to the presence of a nearby quantum critical point.
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Date Issued: 2016-05-23
Identifier: FSU_libsubv1_wos_000376638200005, 10.1103/PhysRevB.93.205141
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

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: 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: 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: 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: 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: 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: 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: 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: 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: 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: Hall Effect Within The Colossal Magnetoresistive Semimetallic State Of Mote2.
Creator: Zhou, Qiong, Rhodes, D., Zhang, Q. R., Tang, S., Schoenemann, R., Balicas, L.
Abstract/Description: Here, we report a systematic study on the Hall effect of the semimetallic state of bulk MoTe2, which was recently claimed to be a candidate for a novel type of Weyl semimetallic state. The temperature (T) dependence of the carrier densities and of their mobilities, as estimated from a numerical analysis based on the isotropic two-carrier model, indicates that its exceedingly large and nonsaturating magnetoresistance may be attributed to a near perfect compensation between the densities of...
Show moreHere, we report a systematic study on the Hall effect of the semimetallic state of bulk MoTe2, which was recently claimed to be a candidate for a novel type of Weyl semimetallic state. The temperature (T) dependence of the carrier densities and of their mobilities, as estimated from a numerical analysis based on the isotropic two-carrier model, indicates that its exceedingly large and nonsaturating magnetoresistance may be attributed to a near perfect compensation between the densities of electrons and holes at low temperatures. A sudden increase in hole density, with a concomitant rapid increase in the electron mobility below T similar to 40 K, leads to comparable densities of electrons and holes at low temperatures suggesting a possible electronic phase transition around this temperature.
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Date Issued: 2016-09-01
Identifier: FSU_libsubv1_wos_000383035100001, 10.1103/PhysRevB.94.121101
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: 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: 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

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

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: 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: Coexistence of Weyl physics and planar defects in the semimetals TaP and TaAs.
Creator: Besara, T., Rhodes, D. A., Chen, K.-W., Das, S., Zhang, Q. R., Sun, J., Zeng, B., Xin, Y., Balicas, L., Baumbach, R. E., Manousakis, E., Singh, D. J., Siegrist, T.
Abstract/Description: We report a structural study of the Weyl semimetals TaAs and TaP, utilizing diffraction and imaging techniques, where we show that they contain a high density of defects, leading to nonstoichiometric single crystals of both semimetals. Despite the observed defects and nonstoichiometry on samples grown using techniques already reported in the literature, de Haas-van Alphen measurements on TaP reveal quantum oscillations and a high carrier mobility, an indication that the crystals are of...
Show moreWe report a structural study of the Weyl semimetals TaAs and TaP, utilizing diffraction and imaging techniques, where we show that they contain a high density of defects, leading to nonstoichiometric single crystals of both semimetals. Despite the observed defects and nonstoichiometry on samples grown using techniques already reported in the literature, de Haas-van Alphen measurements on TaP reveal quantum oscillations and a high carrier mobility, an indication that the crystals are of quality comparable to those reported elsewhere. Electronic structure calculations on TaAs reveal that the position of the Weyl points relative to the Fermi level shift with the introduction of vacancies and stacking faults. In the case of vacancies the Fermi surface becomes considerably altered, while the effect of stacking faults on the electronic structure is to allow the Weyl pockets to remain close to the Fermi surface. The observation of quantum oscillations in a nonstoichiometric crystal and the persistence of Weyl fermion pockets near the Fermi surface in a crystal with stacking faults point to the robustness of these quantum phenomena in these materials.
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Date Issued: 2016-06-27
Identifier: FSU_libsubv1_wos_000378816000007, 10.1103/PhysRevB.93.245152
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: 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

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

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: Intersubband Scattering In N-gaas/algaas Wide Quantum Wells.
Creator: Drichko, I. L., Smirnov, I. Yu, Nestoklon, M. O., Suslov, A. V., Kamburov, D., Baldwin, K. W., Pfeiffer, L. N., West, K. W., Golub, L. E.
Abstract/Description: Slow magneto-oscilations of the conductivity are observed in a 75-nm-wide quantum well at heating of the two-dimensional electrons by a high-intensity surface acoustic wave. These magneto-oscillations are caused by intersubband elastic scattering between the symmetric and asymmetric subbands formed due to an electrostatic barrier in the center of the quantum well. The tunneling splitting between these subbands as well as the intersubband scattering rate are determined.
Date Issued: 2018-02-20
Identifier: FSU_libsubv1_wos_000425492500009, 10.1103/PhysRevB.97.075427
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: Frustrated Magnetism In The Tetragonal Cose Analog Of Superconducting Fese.
Creator: Wilfong, Brandon, Zhou, Xiuquan, Vivanco, Hector, Campbell, Daniel J., Wang, Kefeng, Graf, Dave, Paglione, Johnpierre, Rodriguez, Efrain
Abstract/Description: Recently synthesized metastable tetragonal CoSe, isostructural to the FeSe superconductor, offers a new avenue for investigating systems in close proximity to the iron-based superconductors. We present magnetic and transport property measurements on powders and single crystals of CoSe. High field magnetic susceptibility measurements indicate a suppression of the previously reported 10 K ferromagnetic transition with the magnetic susceptibility, exhibiting time dependence below the proposed...
Show moreRecently synthesized metastable tetragonal CoSe, isostructural to the FeSe superconductor, offers a new avenue for investigating systems in close proximity to the iron-based superconductors. We present magnetic and transport property measurements on powders and single crystals of CoSe. High field magnetic susceptibility measurements indicate a suppression of the previously reported 10 K ferromagnetic transition with the magnetic susceptibility, exhibiting time dependence below the proposed transition. Dynamic scaling analysis of the time dependence yields a critical relaxation time of tau* = 0.064 +/- 0.008 s which in turn yields activation energy E-a(*) = 14.84 +/- 0.59 K and an ideal glass temperature T-0(*) = 8.91 +/- 0.09 K from Vogel-Fulcher analysis. No transition is observed in resistivity and specific heat measurements, but both measurements indicate that CoSe is metallic. These results are interpreted on the basis of CoSe exhibiting frustrated magnetic ordering arising from competing magnetic interactions. Arrott analysis of single crystal magnetic susceptibility has indicated the transition temperature occurs in close proximity to previous reports and that the magnetic moment lies solely in the ab plane. The results have implications for understanding the relationship between magnetism and transport properties in the iron chalcogenide superconductors.
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Date Issued: 2018-03-08
Identifier: FSU_libsubv1_wos_000426901700002, 10.1103/PhysRevB.97.104408
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

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: 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: 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: Absence Of Dirac States In Baznbi2 Induced By Spin-orbit Coupling.
Creator: Ren, Weijun, Wang, Aifeng, Graf, D., Liu, Yu, Zhang, Zhidong, Yin, Wei-Guo, Petrovic, C.
Abstract/Description: We report magnetotransport properties of BaZnBi2 single crystals. Whereas electronic structure features Dirac states, such states are removed from the Fermi level by spin-orbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only three-dimensional, but also with quasi-two-dimensional portions of the Fermi surface. The SOC-induced gap in Dirac states is much larger when compared to isostructural...
Show moreWe report magnetotransport properties of BaZnBi2 single crystals. Whereas electronic structure features Dirac states, such states are removed from the Fermi level by spin-orbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only three-dimensional, but also with quasi-two-dimensional portions of the Fermi surface. The SOC-induced gap in Dirac states is much larger when compared to isostructural SrMnBi2. This suggests that not only long-range magnetic order, but also mass of the alkaline-earth atoms A in ABX(2) (A = alkaline-earth, B = transition-metal, and X = Bi/Sb) are important for the presence of low-energy states obeying the relativistic Dirac equation at the Fermi surface.
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Date Issued: 2018-01-22
Identifier: FSU_libsubv1_wos_000423341500001, 10.1103/PhysRevB.97.035147
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: Temperature-pressure phase diagram of cubic Laves phase Au2Pb.
Creator: Chen, K. W., Graf, D., Besara, T., Gallagher, A., Kikugawa, N., Balicas, L., Siegrist, T., Shekhter, A., Baumbach, R. E.
Abstract/Description: The temperature (T) as a function of pressure (P) phase diagram is reported for the cubic Laves phase compound Au2Pb, which was recently proposed to support linearly dispersing topological bands, together with conventional quadratic bands. At ambient pressure, Au2Pb exhibits several structural phase transitions at T-1 = 97 K, T-2 = 51 K, and T-3 = 40 K with superconductivity below T-c = 1.2 K. Applied pressure results in a rich phase diagram where T-1, T-2, and T-3 evolve strongly with P and...
Show moreThe temperature (T) as a function of pressure (P) phase diagram is reported for the cubic Laves phase compound Au2Pb, which was recently proposed to support linearly dispersing topological bands, together with conventional quadratic bands. At ambient pressure, Au2Pb exhibits several structural phase transitions at T-1 = 97 K, T-2 = 51 K, and T-3 = 40 K with superconductivity below T-c = 1.2 K. Applied pressure results in a rich phase diagram where T-1, T-2, and T-3 evolve strongly with P and a possible new phase is stabilized for P > 0.64 GPa that also supports superconductivity below 1.1 K. These observations suggest that Au2Pb is an ideal system in which to investigate the relationship between structural degrees of freedom, band topology, and resulting anomalous behaviors.
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Date Issued: 2016-01-19
Identifier: FSU_libsubv1_wos_000368486600005, 10.1103/PhysRevB.93.045118
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: Equilibrium, metastability, and hysteresis in a model spin-crossover material with nearest-neighbor antiferromagnetic-like and long-range ferromagnetic-like interactions.
Creator: Rikvold, Per Arne, Brown, Gregory, Miyashita, Seiji, Omand, Conor, Nishino, Masamichi
Abstract/Description: Phase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean- field method for a simplified model of a spin-crossovermaterialwith a two-step transition between the high-spin and low-spin states. This model is a mapping onto a square-lattice S = 1/2 Ising model with antiferromagnetic nearest-neighbor and ferromagnetic Husimi-Temperley ( equivalent-neighbor) long-range interactions. Phase diagrams obtained by the two methods for weak and strong long-range interactions...
Show morePhase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean- field method for a simplified model of a spin-crossovermaterialwith a two-step transition between the high-spin and low-spin states. This model is a mapping onto a square-lattice S = 1/2 Ising model with antiferromagnetic nearest-neighbor and ferromagnetic Husimi-Temperley ( equivalent-neighbor) long-range interactions. Phase diagrams obtained by the two methods for weak and strong long-range interactions are found to be similar. However, for intermediate-strength long-range interactions, the Monte Carlo simulations show that tricritical points decompose into pairs of critical end points and mean-field critical points surrounded by horn-shaped regions of metastability. Hysteresis loops along paths traversing the horn regions are strongly reminiscent of thermal two-step transition loops with hysteresis, recently observed experimentally in several spin-crossover materials. We believe analogous phenomena should be observable in experiments and simulations for many systems that exhibit competition between local antiferromagnetic-like interactions and long-range ferromagnetic-like interactions caused by elastic distortions.
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Date Issued: 2016-02-16
Identifier: FSU_libsubv1_wos_000370244600002, 10.1103/PhysRevB.93.064109
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: 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: 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: Ground-state tuning of metal-insulator transition by compositional variations in BaIr1-xRuxO3 (0 <= x <= 1).
Creator: Yuan, S. J., Butrouna, K., Terzic, J., Zheng, H., Aswartham, S., DeLong, L. E., Ye, Feng, Schlottmann, P., Cao, G.
Abstract/Description: Hexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d(4)) ions for Ir4+ (5d(5)) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting...
Show moreHexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d(4)) ions for Ir4+ (5d(5)) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting state to a robust metallic state. The central findings of this paper are as follows: (1) light Ru doping (0 < x <= 0.15) prompts simultaneous, precipitous drops in both the magnetic ordering temperature T-N and the electrical resistivity, and (2) heavier Ru doping (0.41 <= x <= 0.9) induces a robust metallic state without any long-range magnetic order. All results suggest a critical role of the lattice degrees of freedom in determining the ground state in the heavy transition-metal oxides.
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Date Issued: 2016-04-25
Identifier: FSU_libsubv1_wos_000374950300008, 10.1103/PhysRevB.93.165136
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: 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: 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: Probing The Magnetic Field Dependence Of The Light Hole Transition In Gaas/algaas Quantum Wells Using Optically Pumped Nmr.
Creator: Willmering, Matthew M., Sesti, Erika L., Hayes, Sophia E., Wood, Ryan M., Bowers, Clifford R., Thapa, Sunil K., Stanton, Christopher J., Reyes, Arneil P., Kuhns, Philip, McGill,...
Show moreWillmering, Matthew M., Sesti, Erika L., Hayes, Sophia E., Wood, Ryan M., Bowers, Clifford R., Thapa, Sunil K., Stanton, Christopher J., Reyes, Arneil P., Kuhns, Philip, McGill, Stephen
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Abstract/Description: Optically pumped NMR (OPNMR) of the NMR-active Ga-69/71 species has been shown to be a unique method to probe electronic energy bands in GaAs, with sensitivity to the light hole-to-conduction band transition. This transition is often obscured in other optical measurements such as magnetoabsorption. Using OPNMR, we exploit the hyperfine interaction between conduction band electrons (and their spin states) and nuclear spins, which are detected through phase-sensitive radio-frequency (NMR)...
Show moreOptically pumped NMR (OPNMR) of the NMR-active Ga-69/71 species has been shown to be a unique method to probe electronic energy bands in GaAs, with sensitivity to the light hole-to-conduction band transition. This transition is often obscured in other optical measurements such as magnetoabsorption. Using OPNMR, we exploit the hyperfine interaction between conduction band electrons (and their spin states) and nuclear spins, which are detected through phase-sensitive radio-frequency (NMR) spectroscopy. Measurements were made over a range of external magnetic fields (B-0) in two different labs with separate experimental setups to obtain the magnetic field dependence of the light hole-to-conduction band transition energy. In addition, k . p theory was used to interpret the experimental results, mapping out this specific transition's magnetic field dependence in an AlGaAs/GaAs quantum well. The combination of theory and experiment point to a mixing of valence bands at a field of approximately B-0 = 4.7 T, swapping the dominant character of the absorption transition and, thus, explaining the magnetic field dependence. Lastly, the experimental dependence of the light hole-to-conduction band transition energy on B-0 is found to be less steep compared to the calculated trend, indicating that inclusion of additional effects may be necessary to accurately model the spin-split band structure. The additional insight gained by Ga-69/71 OPNMR about the light hole states will facilitate future testing of more complex band structure models.
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Date Issued: 2018-02-07
Identifier: FSU_libsubv1_wos_000424376500004, 10.1103/PhysRevB.97.075303
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: 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: 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: Wiedemann-Franz law in the underdoped cuprate superconductor YBa2Cu3Oy.
Creator: Grissonnanche, G., Laliberte, F., Dufour-Beausejour, S., Matusiak, M., Badoux, S., Tafti, F. F., Michon, B., Riopel, A., Cyr-Choiniere, O., Baglo, J. C., Ramshaw, B. J., Liang,...
Show moreGrissonnanche, G., Laliberte, F., Dufour-Beausejour, S., Matusiak, M., Badoux, S., Tafti, F. F., Michon, B., Riopel, A., Cyr-Choiniere, O., Baglo, J. C., Ramshaw, B. J., Liang, R., Bonn, D. A., Hardy, W. N., Kraemer, S., LeBoeuf, D., Graf, D., Doiron-Leyraud, N., Taillefer, Louis
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Abstract/Description: The electrical and thermal Hall conductivities of the cuprate superconductor YBa2Cu3Oy, sigma(xy) and kappa(xy), were measured in a magnetic field up to 35 T, at a hole concentration (doping) p = 0.11. In the T = 0 limit, we find that the Wiedemann-Franz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortex-melting field H-vs. This rules out the existence of a vortex liquid at T = 0 and it puts a clear constraint on the nature of the normal...
Show moreThe electrical and thermal Hall conductivities of the cuprate superconductor YBa2Cu3Oy, sigma(xy) and kappa(xy), were measured in a magnetic field up to 35 T, at a hole concentration (doping) p = 0.11. In the T = 0 limit, we find that the Wiedemann-Franz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortex-melting field H-vs. This rules out the existence of a vortex liquid at T = 0 and it puts a clear constraint on the nature of the normal state in underdoped cuprates, in a region of the doping phase diagram where charge-density-wave order is known to exist. As the temperature is raised, the Lorenz ratio, L-xy = kappa(xy)/(sigma T-xy), decreases rapidly, indicating that strong small-q scattering processes are involved.
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Date Issued: 2016-02-22
Identifier: FSU_libsubv1_wos_000370793000005, 10.1103/PhysRevB.93.064513
Format: Citation

Title: Strong correlations generically protect d-wave superconductivity against disorder.
Creator: Tang, Shao, Dobrosavljevic, V., Miranda, E.
Abstract/Description: We address the question of why strongly correlated d-wave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pair-breaking and the normal state transport scattering rates are significantly suppressed by strong correlations effects arising in the proximity to a Mott insulating state. We also show that the correlation-renormalized scattering amplitude is generically enhanced in the...
Show moreWe address the question of why strongly correlated d-wave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pair-breaking and the normal state transport scattering rates are significantly suppressed by strong correlations effects arising in the proximity to a Mott insulating state. We also show that the correlation-renormalized scattering amplitude is generically enhanced in the forward direction, an effect which was previously often ascribed to the specific scattering by charged impurities outside the copper-oxide planes.
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Date Issued: 2016-05-05
Identifier: FSU_libsubv1_wos_000375534600001, 10.1103/PhysRevB.93.195109
Format: Citation

Title: Thermodynamic Constraints On The Amplitude Of Quantum Oscillations.
Creator: Shekhter, Arkady, Modic, K. A., McDonald, R. D., Ramshaw, B. J.
Abstract/Description: Magneto-quantum oscillation experiments in high-temperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B.J. Ramshaw et al., Science 348, 317 (2014); H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010); P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013)]-in support of a quantum-critical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may...
Show moreMagneto-quantum oscillation experiments in high-temperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B.J. Ramshaw et al., Science 348, 317 (2014); H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010); P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013)]-in support of a quantum-critical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may directly indicate the increasing role of quantum fluctuations that suppress the quantum oscillation amplitude through inelastic scattering. We show that the traditional theoretical approaches beyond Lifshitz-Kosevich to calculate the oscillation amplitude in correlated metals result in a contradiction with the third law of thermodynamics and suggest a way to rectify this problem.
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Date Issued: 2017-03-23
Identifier: FSU_libsubv1_wos_000399220000001, 10.1103/PhysRevB.95.121106
Format: Citation

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Yang, Kun (12)	+ -
Graf, D. (11)	+ -
Zhou, H. D. (9)	+ -
Baumbach, R. E. (7)	+ -
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Gong, Shou-Shu (5)	+ -
Petrovic, C. (5)	+ -
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Cao, G. (4)	+ -
Chen, K.-W. (4)	+ -
Kuhns, P. L. (4)	+ -
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Manousakis, Efstratios (3)	+ -
McGill, Stephen A. (3)	+ -
Pfeiffer, L. N. (3)	+ -
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