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 Title
 Jain2/5 Parent Hamiltonian: Structure Of Zero Modes, Dominance Patterns, And Zero Mode Generators.
 Creator
 Chen, Li, Bandyopadhyay, Sumanta, Seidel, Alexander
 Abstract/Description

We analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a fourdimensional twoparticle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about groundstate uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is...
Show moreWe analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a fourdimensional twoparticle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about groundstate uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is given to secondquantized methods, where zero mode properties are derived not from given analytic wave functions, but from a "lattice" Hamiltonian and associated zero mode conditions. This method reveals new insights into the guidingcenter structure of the unprojected Jain2/5 state, in particular, a system of dominance patterns following a "generalized Pauli principle," which establishes a complete onetoone correspondence with the edge mode counting. We also identify onebody operators that function as generators of zero modes.
Show less  Date Issued
 20170531
 Identifier
 FSU_libsubv1_wos_000402463500001, 10.1103/PhysRevB.95.195169
 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 twodimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by xray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specificheat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin1/2) and Ni2+ (spin1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin5/2) ions...
Show moreThe geometrically frustrated twodimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by xray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specificheat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin1/2) and Ni2+ (spin1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin5/2) ions with a large spin number exhibits antiferromagnetic (AFM) ordering. We ascribe these spinnumbermanipulated ground states to the competition between the AFM B'OOB' and FM B'OBOB' superexchange interactions. (ii) The chemical pressure introduced into the Cocontaining samples through the replacement of differentsize 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.
Show less  Date Issued
 20170525
 Identifier
 FSU_libsubv1_wos_000401998500003, 10.1103/PhysRevB.95.174438
 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 WHMtype 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 spinorbit 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 WHMtype 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 spinorbit 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 spinorbit coupling and lattice constants in the WHM system.
Show less  Date Issued
 20170522
 Identifier
 FSU_libsubv1_wos_000402003700006, 10.1103/PhysRevB.95.205134
 Format
 Citation
 Title
 Possible Nematic Spin Liquid In Spin1 Antiferromagnetic System On The Square Lattice: Implications For The Nematic Paramagnetic State Of Fese.
 Creator
 Gong, ShouShu, 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 spin1 system with bilinearbiquadratic interactions using an unbiased largescale 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 spin1 system with bilinearbiquadratic interactions using an unbiased largescale 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.
Show less  Date Issued
 20170519
 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 highquality 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 highquality 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.
Show less  Date Issued
 20170515
 Identifier
 FSU_libsubv1_wos_000401449700001, 10.1103/PhysRevB.95.195129
 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 chargecarrier concentrations. At low chargecarrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high chargecarrier 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 chargecarrier concentrations. At low chargecarrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high chargecarrier 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 HikamiLarkinNagaoka formula. At high chargecarrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low chargecarrier 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.
Show less  Date Issued
 20170508
 Identifier
 FSU_libsubv1_wos_000401229000004, 10.1103/PhysRevB.95.195113
 Format
 Citation
 Title
 Magnetic Ground States And Magnetodielectric Effect In Rcr(bo3)(2) (r = Y And Ho).
 Creator
 Sinclair, R., Zhou, H. D., Lee, M., Choi, S., Li, G., Hong, T., Calder, S.
 Abstract/Description

The layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 89 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 23 T is applied below TN, the Cr3+...
Show moreThe layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 89 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 23 T is applied below TN, the Cr3+ spins in the Y compound and both the Cr3+ and Ho3+ spins in the Ho compound order in a ferromagnetic state; (iii) both samples exhibit dielectric constant anomalies around the transition temperature and critical field, but the Ho compound displays a much stronger magnetodielectric response. We speculate that this is due to the magnetostriction, which depends on both the Cr3+ and the Ho3+ ions' ordering in the Ho compound. Moreover, by using linear spinwave theory to simulate the inelastic neutron scattering data, we estimated the Y compound's intralayer and interlayer exchange strengths as ferromagnetic J(1) = 0.12 meV and antiferromagnetic J(2) = 0.014 meV, respectively. The competition between different kinds of superexchange interactions results in the ferromagnetic intralayer interaction.
Show less  Date Issued
 20170508
 Identifier
 FSU_libsubv1_wos_000401223700002, 10.1103/PhysRevB.95.174410
 Format
 Citation
 Title
 Effects Of Uniaxial Pressure On The Quantum Tunneling Of Magnetization In A Highsymmetry Mn12 Singlemolecule 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 singlemolecule 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 highsymmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH singlemolecule magnet as a function of uniaxial pressure...
Show moreThe symmetry of singlemolecule 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 highsymmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH singlemolecule 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 resonanttunneling 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 secondorder axial anisotropy parameter as well as either the fourthorder axial or fourthorder 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 symmetrybreaking distortion of the molecule.
Show less  Date Issued
 20170504
 Identifier
 FSU_libsubv1_wos_000400657600001, 10.1103/PhysRevB.95.184403
 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 Asite spinel material CoAl2O4 is a physical realization of the frustrated diamondlattice antiferromagnet, a model in which unique incommensurate or "spinspiralliquid" ground states are predicted. Our previous singlecrystal neutron scattering study instead classified it as a "kinetically inhibited" antiferromagnet, where the longranged correlations of a collinear Neel ground state are blocked by the freezing of domainwall motion below a firstorder phase transition at T* = 6.5 K....
Show moreThe Asite spinel material CoAl2O4 is a physical realization of the frustrated diamondlattice antiferromagnet, a model in which unique incommensurate or "spinspiralliquid" ground states are predicted. Our previous singlecrystal neutron scattering study instead classified it as a "kinetically inhibited" antiferromagnet, where the longranged correlations of a collinear Neel ground state are blocked by the freezing of domainwall motion below a firstorder 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 lowtemperature 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 shortranged 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 TN = 39 K. Direct comparison between the two compounds indicates that CoAl2O4 is unique, not in the nature of hightemperature 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 nextnearestneighbor exchange.
Show less  Date Issued
 20161117
 Identifier
 FSU_libsubv1_wos_000387887100005, 10.1103/PhysRevB.94.184422
 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

Pumpprobe optical spectroscopy was used to investigate proposed chargecarrier multiplication via impact ionization in the M1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the bandgap 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 morePumpprobe optical spectroscopy was used to investigate proposed chargecarrier multiplication via impact ionization in the M1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the bandgap 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.
Show less  Date Issued
 20161017
 Identifier
 FSU_libsubv1_wos_000386097100004, 10.1103/PhysRevB.94.155129
 Format
 Citation
 Title
 Evidence For Correlated Dynamics Near The Berezinskiikosterlitzthoulesslike Transition In Highly Underdoped La2xsrxcuo4.
 Creator
 Shi, Zhenzhong, Shi, Xiaoyan, Popovic, Dragana
 Abstract/Description

A lowfrequency resistance noise study in highly underdoped thick films of La2xSrxCuO4 (x = 0.07 and 0.08) reveals slow, correlated dynamics and breaking of ergodicity near the superconducting transition of the BerezinskiiKosterlitzThouless type. The observed correlated behavior is strongly suppressed by disorder.
 Date Issued
 20161005
 Identifier
 FSU_libsubv1_wos_000385239900002, 10.1103/PhysRevB.94.134503
 Format
 Citation
 Title
 Electrical Transport Properties Of Singlecrystal Cab6, Srb6, And Bab6.
 Creator
 Stankiewicz, Jolanta, Rosa, Priscila F. S., Schlottmann, Pedro, Fisk, Zachary
 Abstract/Description

The electrical resistivity and Hall effect of alkalineearthmetal 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 variablevalence 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 alkalineearthmetal 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 variablevalence 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.
Show less  Date Issued
 20160922
 Identifier
 FSU_libsubv1_wos_000383865700005, 10.1103/PhysRevB.94.125141
 Format
 Citation
 Title
 Nonisinglike Twodimensional 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 Tc similar to 3.5 and similar to 4.7K, respectively. Disorder was claimed to lead to the extremely large upper critical fields (Hc2) observed in related compounds. Despite the presence of disorder and heavier elements, Hc2s 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 Tc similar to 3.5 and similar to 4.7K, respectively. Disorder was claimed to lead to the extremely large upper critical fields (Hc2) observed in related compounds. Despite the presence of disorder and heavier elements, Hc2s 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 Hc2 alpha (1T/Tc)(1/2), which in monolayers of transition metal dichalcogenides is claimed to be evidence for an Ising paired superconducting state resulting from strong spinorbit coupling. This anomalous T dependence indicates that the superconducting state of Nb3PdxSe7 is quasitwodimensional in nature. This is further supported by a nearly divergent anisotropy in uppercritical fields, i.e., gamma= Hc2(b)/Hc2(a)', upon approaching Tc. Hence, in Nb3PdxSe7 the increase of Tc 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 fieldinduced pinning of the spin to the lattice as a possible mechanism for decoupling the superconducting planes.
Show less  Date Issued
 20160912
 Identifier
 FSU_libsubv1_wos_000383138700005, 10.1103/PhysRevB.94.094511
 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 magneticfieldinduced changes in interlayer conduction are also present in layered bismuthbased materials with a zeroenergy line in momentum space created by the staggered alkaline earth atoms.
Show less  Date Issued
 20160912
 Identifier
 FSU_libsubv1_wos_000383145300004, 10.1103/PhysRevB.94.125118
 Format
 Citation
 Title
 Magnetic Phases Of The Quasitwodimensional 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 Cu63,Cu65 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 Cu63,Cu65 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 2D3D transition is hysteretic in field and temperature. Lineshape analysis reveals several possible magnetic structures existing within individual planes for different phases of CuCrO2. Within certain regions on the magnetic HT phase diagram of CuCrO2 a 3D magnetic ordering with tensor order parameter is expected.
Show less  Date Issued
 20160912
 Identifier
 FSU_libsubv1_wos_000383138700003, 10.1103/PhysRevB.94.094410
 Format
 Citation
 Title
 Determination Of The Effective Kinematic Viscosity For The Decay Of Quasiclassical Turbulence In Superfluid He4.
 Creator
 Gao, J., Guo, W., Vinen, W. F.
 Abstract/Description

The energy dissipation of quasiclassical homogeneous turbulence in superfluid He4 (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 highReynoldsnumber turbulence experiments and model testing that use He II...
Show moreThe energy dissipation of quasiclassical homogeneous turbulence in superfluid He4 (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 highReynoldsnumber 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 flowvisualization technique and L(t) via secondsound 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).
Show less  Date Issued
 20160901
 Identifier
 FSU_libsubv1_wos_000383033500004, 10.1103/PhysRevB.94.094502
 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 twocarrier 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 twocarrier 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.
Show less  Date Issued
 20160901
 Identifier
 FSU_libsubv1_wos_000383035100001, 10.1103/PhysRevB.94.121101
 Format
 Citation
 Title
 Structure And Ferromagnetic Instability Of The Oxygendeficient Srtio3 Surface.
 Creator
 Ghosh, Soham S., Manousakis, Efstratios
 Abstract/Description

SrTiO3 (STO) is the substrate of choice to grow oxide thin films and oxide heterojunctions, which can form quasitwodimensional electronic phases that exhibit a wealth of phenomena, and thus a workhorse in the emerging field of metaloxide electronics. Hence, it is of great importance to know the exact character of the STO surface itself under various oxygen environments. Using density functional theory within the spin generalized gradient approximation we have investigated the structural,...
Show moreSrTiO3 (STO) is the substrate of choice to grow oxide thin films and oxide heterojunctions, which can form quasitwodimensional electronic phases that exhibit a wealth of phenomena, and thus a workhorse in the emerging field of metaloxide electronics. Hence, it is of great importance to know the exact character of the STO surface itself under various oxygen environments. Using density functional theory within the spin generalized gradient approximation we have investigated the structural, electronic, and magnetic properties of the oxygendeficient STO surface. We find that the surface oxygen vacancies order in periodic arrays giving rise to surface magnetic moments and a quasitwodimensional electron gas in the occupied Ti 3d orbitals. The surface confinement, the oxygenvacancy ordering, and the octahedra distortions give rise to spinpolarized t(2g) dispersive subbands; their energy split near the Brillouin zone center acts as an effective Zeeman term, which, when we turn on a Rashba interaction, produces bands with momentumspin correlations similar to those recently discovered on oxygendeficient STO surface.
Show less  Date Issued
 20160824
 Identifier
 FSU_libsubv1_wos_000381890100001, 10.1103/PhysRevB.94.085141
 Format
 Citation
 Title
 Melting Of Wigner Crystal In Highmobility Ngaas/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 highfrequency conductance of highmobility nGaAs/AlGaAs heterostructures was determined in magnetic fields 1218 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 highfrequency conductance of highmobility nGaAs/AlGaAs heterostructures was determined in magnetic fields 1218 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 sodefined melting temperature on the electron filling factor.
Show less  Date Issued
 20160815
 Identifier
 FSU_libsubv1_wos_000381482600007, 10.1103/PhysRevB.94.075420
 Format
 Citation
 Title
 Variational Monte Carlo Study Of Chiral Spin Liquid In Quantum Antiferromagnet On The Triangular Lattice.
 Creator
 Hu, WenJun, Gong, ShouShu, Sheng, D. N.
 Abstract/Description

By using Gutzwiller projected fermionic wave functions and variational Monte Carlo technique, we study the spin1/2 Heisenberg model with the firstneighbor (J(1)), secondneighbor (J(2)), and additional scalar chiral interaction J(chi)S(i) . (Sj x Sk) on the triangular lattice. In the nonmagnetic phase of the J(1)J(2) triangular model with 0.08 less than or similar to J(2)/J(1) less than or similar to 0.16, recent densitymatrix renormalization group (DMRG) studies [Zhu and White, Phys....
Show moreBy using Gutzwiller projected fermionic wave functions and variational Monte Carlo technique, we study the spin1/2 Heisenberg model with the firstneighbor (J(1)), secondneighbor (J(2)), and additional scalar chiral interaction J(chi)S(i) . (Sj x Sk) on the triangular lattice. In the nonmagnetic phase of the J(1)J(2) triangular model with 0.08 less than or similar to J(2)/J(1) less than or similar to 0.16, recent densitymatrix renormalization group (DMRG) studies [Zhu and White, Phys. Rev. B 92, 041105(R) (2015) and Hu, Gong, Zhu, and Sheng, Phys. Rev. B 92, 140403(R) (2015)] find a possible gapped spin liquid with the signal of a competition between a chiral and a Z(2) spin liquid. Motivated by the DMRG results, we consider the chiral interaction J(chi)S(i) . (Sj x Sk) as a perturbation for this nonmagnetic phase. We find that with growing J(chi), the gapless U(1) Dirac spin liquid, which has the best variational energy for J(chi) = 0, exhibits the energy instability towards a gapped spin liquid with nontrivial magnetic fluxes and nonzero chiral order. We calculate topological Chern number and groundstate degeneracy, both of which identify this flux state as the chiral spin liquid with fractionalized Chern number C = 1/2 and twofold topological degeneracy. Our results indicate a positive direction to stabilize a chiral spin liquid near the nonmagnetic phase of the J(1)J(2) triangular model.
Show less  Date Issued
 20160815
 Identifier
 FSU_libsubv1_wos_000381482600002, 10.1103/PhysRevB.94.075131
 Format
 Citation
 Title
 Emergent Quasionedimensionality In A Kagome Magnet: A Simple Route To Complexity.
 Creator
 Gong, ShouShu, Zhu, Wei, Yang, Kun, Starykh, Oleg A., Sheng, D. N., Balents, Leon
 Abstract/Description

We study the groundstate phase diagram of the quantum spin1/2 Heisenberg model on the kagome lattice with first(J(1) < 0), second(J(2) < 0), and thirdneighbor interactions (J(d) > 0) by means of analytical lowenergy field theory and numerical densitymatrix 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 groundstate phase diagram of the quantum spin1/2 Heisenberg model on the kagome lattice with first(J(1) < 0), second(J(2) < 0), and thirdneighbor interactions (J(d) > 0) by means of analytical lowenergy field theory and numerical densitymatrix 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 longranged 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 twodimensional quantum antiferromagnet. We find no evidence of either the onedimensional gapless spin liquid or the chiral spin liquids, which were previously suggested by parton meanfield theories.
Show less  Date Issued
 20160727
 Identifier
 FSU_libsubv1_wos_000381482700001, 10.1103/PhysRevB.94.035154
 Format
 Citation
 Title
 Spin correlations and topological entanglement entropy in a nonAbelian spinone spin liquid.
 Creator
 Wildeboer, Julia, Bonesteel, N. E.
 Abstract/Description

We analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the...
Show moreWe analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the torus. We show that spin correlations for different states in this space become indistinguishable for large system size. We also calculate the Renyi entanglement entropy for different system partitions to extract the topological entanglement entropy and provide evidence that the topological order of the lattice spinliquid state is the same as that of the continuum MooreRead state from which it is constructed.
Show less  Date Issued
 20160718
 Identifier
 FSU_libsubv1_wos_000380104300008, 10.1103/PhysRevB.94.045125
 Format
 Citation
 Title
 Probing 5 f state configurations in URu2Si2 with U LIIIedge resonant xray emission spectroscopy.
 Creator
 Booth, C. H., Medling, S. A., Tobin, J. G., Baumbach, R. E., Bauer, E. D., Sokaras, D., Nordlund, D., Weng, T.C.
 Abstract/Description

Resonant xray emission spectroscopy (RXES) was employed at the U LIII absorption edge and the Lalpha 1 emission line to explore the 5f occupancy, n(f), and the degree of 5f orbital delocalization in the hiddenorder compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alphaU, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with n(f) = 2.87 +/ 0.08, and does not change with temperature down to 10 K within the estimated error....
Show moreResonant xray emission spectroscopy (RXES) was employed at the U LIII absorption edge and the Lalpha 1 emission line to explore the 5f occupancy, n(f), and the degree of 5f orbital delocalization in the hiddenorder compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alphaU, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with n(f) = 2.87 +/ 0.08, and does not change with temperature down to 10 K within the estimated error. These results place further constraints on theoretical explanations of the hidden order, especially those requiring a localized f(2) ground state.
Show less  Date Issued
 20160715
 Identifier
 FSU_libsubv1_wos_000379651600007, 10.1103/PhysRevB.94.045121
 Format
 Citation
 Title
 Interactiondriven Fractional Quantum Hall State Of Hardcore Bosons On Kagome Lattice At Onethird 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 interactiongenerated topological phases, without the requirement of a nontrivial invariant encoded in singleparticle 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 interactiongenerated topological phases, without the requirement of a nontrivial invariant encoded in singleparticle wave function or band structure, can significantly extend the class of topological materials and is thus of great importance. Here, we show an interactiondriven topological phase emerging in an extended BoseHubbard 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 stateoftheart densitymatrix 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 groundstate degeneracy, edge excitations, and anyonic quasiparticle statistics. Our work paves a way to finding an interactioninduced topological phase at the phase boundary of conventionally ordered solid phases.
Show less  Date Issued
 20160713
 Identifier
 FSU_libsubv1_wos_000379502800001, 10.1103/PhysRevB.94.035129
 Format
 Citation
 Title
 Crystal Structure And Partial Isinglike 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 xray 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 twodimensional (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 xray 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 twodimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a threedimensional 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 Isinglike magnetic ordering. Consequently, two succeeding transitions under magnetic field are observed in the ac susceptibility, which are associated with flipping each Dy3+ spin independently.
Show less  Date Issued
 20160712
 Identifier
 FSU_libsubv1_wos_000379500900004, 10.1103/PhysRevB.94.024413
 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 Haasvan 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 Haasvan 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.
Show less  Date Issued
 20160627
 Identifier
 FSU_libsubv1_wos_000378816000007, 10.1103/PhysRevB.93.245152
 Format
 Citation
 Title
 Simultaneous Metalinsulator And Antiferromagnetic Transitions In Orthorhombic Perovskite Iridate Sr0.94ir0.78o2.68 Single Crystals.
 Creator
 Zheng, H., Terzic, J., Ye, Feng, Wan, X. G., Wang, D., Wang, Jinchen, Wang, Xiaoping, Schlottmann, P., Yuan, S. J., Cao, G.
 Abstract/Description

The orthorhombic perovskite SrIrO3 is a semimetal, an intriguing exception in iridates where the strong spinorbit interaction coupled with electron correlations tends to impose an insulating state. We report results of our investigation of bulk singlecrystal Sr0.94Ir0.78O2.68 or Irdeficient, orthorhombic perovskite SrIrO3. It retains the same crystal structure as stoichiometric SrIrO3 but exhibits a sharp, simultaneous antiferromagnetic (AFM) and metalinsulator (MI) transition occurring...
Show moreThe orthorhombic perovskite SrIrO3 is a semimetal, an intriguing exception in iridates where the strong spinorbit interaction coupled with electron correlations tends to impose an insulating state. We report results of our investigation of bulk singlecrystal Sr0.94Ir0.78O2.68 or Irdeficient, orthorhombic perovskite SrIrO3. It retains the same crystal structure as stoichiometric SrIrO3 but exhibits a sharp, simultaneous antiferromagnetic (AFM) and metalinsulator (MI) transition occurring in the basalplane resistivity at 185 K. Above it, the basalplane resistivity features an extended regime of almost linear temperature dependence up to 800 K but the strong electronic anisotropy renders an insulating behavior in the outofplane resistivity. The Hall resistivity undergoes an abrupt sign change and grows below 40 K, which along with the Sommerfeld constant of 20 mJ/mol K2 suggests a multiband effect. All results including our firstprinciples calculations underscore a delicacy of the paramagnetic, metallic state in SrIrO3 that is in close proximity to an AFM insulating state. The contrasting ground states in isostructural Sr0.94Ir0.78O2.68 and SrIrO3 illustrate a critical role of lattice distortions and Ir deficiency in rebalancing the ground state in the iridates. Finally, the concurrent AFM and MI transitions reveal a direct correlation between the magnetic transition and formation of an activation gap in the iridate, which is conspicuously absent in Sr2IrO4.
Show less  Date Issued
 20160627
 Identifier
 FSU_libsubv1_wos_000378813800008, 10.1103/PhysRevB.93.235157
 Format
 Citation
 Title
 Persistence Of Slow Fluctuations In The Overdoped Regime Of Ba(fe1xrhx)(2)as2 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(Fe1xRhx)(2)As2 superconductors. Measurements of the As75 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 shortrange 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(Fe1xRhx)(2)As2 superconductors. Measurements of the As75 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 shortrange 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.
Show less  Date Issued
 20160623
 Identifier
 FSU_libsubv1_wos_000378305600003, 10.1103/PhysRevB.93.224517
 Format
 Citation
 Title
 Superconducting Subphase In The Layered Perovskite Ruthenate Sr2ruo4 In A Parallel Magnetic Field.
 Creator
 Kikugawa, Naoki, Terashima, Taichi, Uji, Shinya, Sugii, Kaori, Maeno, Yoshiteru, Graf, David, Baumbach, Ryan, Brooks, James
 Abstract/Description

Magnetic torque measurements using a microcantilever have been performed to investigate the superconducting phase of Sr2RuO4 down to 40 mK. For highquality single crystals with the transition temperature (Tc) of 1.481.49 K, an abrupt jump of the torque signal is found near 1.5 T in field parallel to the conducting RuO2 planes below similar to 0.8K. The jump corresponds to the first order transition recently revealed by magnetocaloric and magnetization measurements [Yonezawa et al., Phys....
Show moreMagnetic torque measurements using a microcantilever have been performed to investigate the superconducting phase of Sr2RuO4 down to 40 mK. For highquality single crystals with the transition temperature (Tc) of 1.481.49 K, an abrupt jump of the torque signal is found near 1.5 T in field parallel to the conducting RuO2 planes below similar to 0.8K. The jump corresponds to the first order transition recently revealed by magnetocaloric and magnetization measurements [Yonezawa et al., Phys. Rev. Lett. 110, 077003 (2013); Kittaka et al., Phys. Rev. B 90, 220502(R) (2014)]. Furthermore, weak diamagnetic and irreversible signals are found to persist above the first order transition up to 1.85 T. The result indicates the presence of a subphase boundary separating lowand highfield phases in the superconducting phase. The highfield subphase disappears when the field is tilted from the conducting planes only by a few degrees. Quantum oscillation measurements are also reported to clarify the strong samplequality dependence of the highfield subphase.
Show less  Date Issued
 20160531
 Identifier
 FSU_libsubv1_wos_000376908700006, 10.1103/PhysRevB.93.184513
 Format
 Citation
 Title
 Physical properties of the Ce2MAl7Ge4 heavyfermion compounds (M = Co, Ir, Ni, Pd).
 Creator
 Ghimire, N. J., Cary, S. K., Eley, S., Wakeham, N. A., Rosa, P. F. S., AlbrechtSchmitt, T., Lee, Y., Janoschek, M., Brown, C. M., Civale, L., Thompson, J. D., Ronning, F., Bauer, E. D.
 Abstract/Description

We report the synthesis, crystal structure, and characterization by means of singlecrystal xray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavyfermion 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 GeAl and MAlGe blocks. Ce2CoAl7Ge4, Ce2IrAl7Ge4, and Ce2NiAl7Ge4 order...
Show moreWe report the synthesis, crystal structure, and characterization by means of singlecrystal xray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavyfermion 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 GeAl and MAlGe blocks. Ce2CoAl7Ge4, Ce2IrAl7Ge4, and Ce2NiAl7Ge4 order magnetically below TM = 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 nonFermi liquid behavior, possibly due to the presence of a nearby quantum critical point.
Show less  Date Issued
 20160523
 Identifier
 FSU_libsubv1_wos_000376638200005, 10.1103/PhysRevB.93.205141
 Format
 Citation
 Title
 Striped Quantum Hall State In A Halffilled Landau Level.
 Creator
 Wan, Xin, Yang, Kun
 Abstract/Description

The nature of the fractional quantum Hall state at Landau level filling factor 5/2 remains elusive despite intensive experimental and theoretical work. While the leading theoretical candidates are MooreRead Pfaffian (Pf) and its particlehole conjugate antiPfaffian (APf), neither received unambiguous experimental support. We show that a state that is intermediate between them, made of alternating stripes of Pf and APf in the bulk, is a viable candidate. Such a state is shown to be...
Show moreThe nature of the fractional quantum Hall state at Landau level filling factor 5/2 remains elusive despite intensive experimental and theoretical work. While the leading theoretical candidates are MooreRead Pfaffian (Pf) and its particlehole conjugate antiPfaffian (APf), neither received unambiguous experimental support. We show that a state that is intermediate between them, made of alternating stripes of Pf and APf in the bulk, is a viable candidate. Such a state is shown to be incompressible and thus a charge insulator in the bulk, but a heat conductor due to the presence of gapless neutral bulk modes. We argue that the properties of such a state are consistent with existing numerical and experimental work, and discuss possible experimental probes of its presence.
Show less  Date Issued
 20160523
 Identifier
 FSU_libsubv1_wos_000376638200001, 10.1103/PhysRevB.93.201303
 Format
 Citation
 Title
 Strong correlations generically protect dwave superconductivity against disorder.
 Creator
 Tang, Shao, Dobrosavljevic, V., Miranda, E.
 Abstract/Description

We address the question of why strongly correlated dwave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pairbreaking 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 correlationrenormalized scattering amplitude is generically enhanced in the...
Show moreWe address the question of why strongly correlated dwave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pairbreaking 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 correlationrenormalized 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 copperoxide planes.
Show less  Date Issued
 20160505
 Identifier
 FSU_libsubv1_wos_000375534600001, 10.1103/PhysRevB.93.195109
 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, highfrequency electron spin resonance, Li7 nuclear magnetic resonance, and zerofield 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 twostage symmetry breaking: a magnetostructural phase transition with subsequent antiferromagnetic ordering. We find a disparate symmetry breaking...
Show moreWe present magnetic susceptibility, dielectric constant, highfrequency electron spin resonance, Li7 nuclear magnetic resonance, and zerofield 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 twostage 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 TS = 15.2 K, followed by the magnetic ordering at Tm = 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 TS = 17.6 K and the second antiferromagnetic ordering at Tm = 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 spinlattice coupling, thus stabilizing longrange magnetic ordering against a nonmagnetic singlet.
Show less  Date Issued
 20160502
 Identifier
 FSU_libsubv1_wos_000375525700002, 10.1103/PhysRevB.93.174402
 Format
 Citation
 Title
 Cyclotron decay time of a twodimensional electron gas from 0.4 to 100 K.
 Creator
 Curtis, Jeremy A., Tokumoto, Takahisa, Hatke, A. T., Cherian, Judy G., Reno, John L., McGill, Stephen A., Karaiskaj, Denis, Hilton, David J.
 Abstract/Description

We have studied the cyclotron decay time of a Landauquantized twodimensional electron gas as a function of temperature (0.4100 K) at a fixed magnetic field (+/ 1.25 T) using terahertz timedomain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V1 s(1) and a carrier concentration of n(s) = 2 x 10(11) cm(2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may...
Show moreWe have studied the cyclotron decay time of a Landauquantized twodimensional electron gas as a function of temperature (0.4100 K) at a fixed magnetic field (+/ 1.25 T) using terahertz timedomain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V1 s(1) and a carrier concentration of n(s) = 2 x 10(11) cm(2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may result from both dissipative processes as well as a decrease in n(s) below 1.5K. Shubnikovde Haas characterization determines a quantum lifetime, tau(q) = 1.1 ps, which is significantly faster than the corresponding dephasing time, tau(s) = 66.4 ps, in our cyclotron data. This is consistent with smallangle scattering as the dominant contribution in this sample, where scattering angles below theta <= 13 degrees. do not efficiently contribute to dephasing. Above 50 K, the cyclotron oscillations show a strong reduction in both the oscillation amplitude and lifetime that result from polar optical phonon scattering.
Show less  Date Issued
 20160429
 Identifier
 FSU_libsubv1_wos_000375202600004, 10.1103/PhysRevB.93.155437
 Format
 Citation
 Title
 Groundstate tuning of metalinsulator transition by compositional variations in BaIr1xRuxO3 (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 spinorbit 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 spinorbit 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 TN and the electrical resistivity, and (2) heavier Ru doping (0.41 <= x <= 0.9) induces a robust metallic state without any longrange magnetic order. All results suggest a critical role of the lattice degrees of freedom in determining the ground state in the heavy transitionmetal oxides.
Show less  Date Issued
 20160425
 Identifier
 FSU_libsubv1_wos_000374950300008, 10.1103/PhysRevB.93.165136
 Format
 Citation
 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 twodimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intraLandau level dynamical response in the longwavelength 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 twodimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intraLandau level dynamical response in the longwavelength 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 timedependent 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 straininduced 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.
Show less  Date Issued
 20160415
 Identifier
 FSU_libsubv1_wos_000374297500001, 10.1103/PhysRevB.93.161302
 Format
 Citation
 Title
 Electronhole asymmetry, Dirac fermions, and quantum magnetoresistance in BaMnBi2.
 Creator
 Li, Lijun, Wang, Kefeng, Graf, D., Wang, Limin, Wang, Aifeng, Petrovic, C.
 Abstract/Description

We report twodimensional quantum transport and Dirac fermions in BaMnBi2 single crystals. BaMnBi2 is a layered bad metal with highly anisotropic conductivity and magnetic order below 290 K. Magnetotransport properties, nonzero Berry phase, small cyclotronmass, and the firstprinciples band structure calculations indicate the presence of Dirac fermions in Bi square nets. Quantum oscillations in the Hall channel suggest the presence of both electron and hole pockets, whereas Dirac and...
Show moreWe report twodimensional quantum transport and Dirac fermions in BaMnBi2 single crystals. BaMnBi2 is a layered bad metal with highly anisotropic conductivity and magnetic order below 290 K. Magnetotransport properties, nonzero Berry phase, small cyclotronmass, and the firstprinciples band structure calculations indicate the presence of Dirac fermions in Bi square nets. Quantum oscillations in the Hall channel suggest the presence of both electron and hole pockets, whereas Dirac and parabolic states coexist at the Fermi level.
Show less  Date Issued
 20160328
 Identifier
 FSU_libsubv1_wos_000372799100001, 10.1103/PhysRevB.93.115141
 Format
 Citation
 Title
 Charge avalanches and depinning in the Coulomb glass: The role of longrange 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 farfromequilibrium metastable states of a threedimensional 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 particleconserving dynamics, scalefree systemspanning avalanches are observed only at the...
Show moreWe explore the stability of farfromequilibrium metastable states of a threedimensional 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 particleconserving dynamics, scalefree systemspanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent shortrange model, highlighting the key importance of longrange interactions for nonequilibrium dynamics of Coulomb glasses.
Show less  Date Issued
 20160324
 Identifier
 FSU_libsubv1_wos_000372712000002, 10.1103/PhysRevB.93.094429
 Format
 Citation
 Title
 Probing critical surfaces in momentum space using realspace entanglement entropy: Bose versus Fermi.
 Creator
 Lai, HsinHua, Yang, Kun
 Abstract/Description

A codimensionone 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 realspace...
Show moreA codimensionone 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 realspace 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: Slog(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.
Show less  Date Issued
 20160323
 Identifier
 FSU_libsubv1_wos_000372716500001, 10.1103/PhysRevB.93.121109
 Format
 Citation
 Title
 Phase separation and superparamagnetism in the martensitic phase of Ni50xCoxMn40Sn10.
 Creator
 Yuan, S., Kuhns, P. L., Reyes, A. P., Brooks, J. S., Hoch, M. J. R., Srivastava, V., James, R. D., Leighton, C.
 Abstract/Description

Ni50xCoxMn40Sn10 shape memory alloys in the approximate range 5 <= x <= 8 display desirable properties for applications as well as intriguing magnetism. These offstoichiometric Heusler alloys undergo a martensitic phase transformation at a temperature TM of 300400 K, from ferromagnetic (FM) to nonferromagnetic, with unusually low thermal hysteresis and a large change in magnetization. The low temperature magnetic structures in the martensitic phase of such alloys, which are distinctly...
Show moreNi50xCoxMn40Sn10 shape memory alloys in the approximate range 5 <= x <= 8 display desirable properties for applications as well as intriguing magnetism. These offstoichiometric Heusler alloys undergo a martensitic phase transformation at a temperature TM of 300400 K, from ferromagnetic (FM) to nonferromagnetic, with unusually low thermal hysteresis and a large change in magnetization. The low temperature magnetic structures in the martensitic phase of such alloys, which are distinctly inhomogeneous, are of great interest but are not well understood. Our present use of spin echo nuclear magnetic resonance in the large hyperfine fields at Mn55 sites provides compelling evidence that nanoscale magnetic phase separation into FM and antiferromagnetic (AFM) regions occurs below TM in alloys with x in the range 0 to 7. At finite Co substitution, the FM regions are found to be of two distinct types, corresponding to high and low local concentrations of Co on Ni sites. Estimates of the size distributions of both the FM and AFM nanoregions have been made. At x = 7, the AFM component is not longrange ordered, even below 4 K, and is quite different from the AFM component found at x = 0; by x = 14, the FM phase is completely dominant. Of particular interest, we find for x = 7 that field cooling leads to dramatic changes in the AFM regions. These findings provide insight into the origins of magnetic phase separation and superparamagnetism in these complex alloys, particularly their intrinsic exchange bias, which is of considerable current interest.
Show less  Date Issued
 20160321
 Identifier
 FSU_libsubv1_wos_000372711200004, 10.1103/PhysRevB.93.094425
 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 twodimensional 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 singleparticle 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 twodimensional 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 singleparticle 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 timereversal symmetry at specific rational filling fractions.
Show less  Date Issued
 20160316
 Identifier
 FSU_libsubv1_wos_000372413000006, 10.1103/PhysRevB.93.125126
 Format
 Citation
 Title
 Quantum antiferromagnetic Heisenberg halfoddinteger spin model as the entanglement Hamiltonian of the integerspin AffleckKennedyLiebTasaki states.
 Creator
 Rao, WenJia, Zhang, GuangMing, Yang, Kun
 Abstract/Description

Applying a symmetric bulk bipartition to the onedimensional AffleckKennedyLiebTasaki valencebond solid (VBS) states for the integer spinS Haldane gapped phase, we can create an array of fractionalized spinS/2 edge states with the super unit cell l in the reduced bulk system, and the topological properties encoded in the VBS wave functions can be revealed. The entanglement Hamiltonian (EH) with even l corresponds to the quantum antiferromagnetic Heisenberg spinS/2 model. For the even...
Show moreApplying a symmetric bulk bipartition to the onedimensional AffleckKennedyLiebTasaki valencebond solid (VBS) states for the integer spinS Haldane gapped phase, we can create an array of fractionalized spinS/2 edge states with the super unit cell l in the reduced bulk system, and the topological properties encoded in the VBS wave functions can be revealed. The entanglement Hamiltonian (EH) with even l corresponds to the quantum antiferromagnetic Heisenberg spinS/2 model. For the even integer spins, the EH still describes the Haldane gapped phase. For the odd integer spins, however, the EH just corresponds to the quantum antiferromagnetic Heisenberg halfodd integerspin model with spinon excitations, characterizing the critical point separating the topological Haldane phase from the trivial gapped phase. Our results thus demonstrate that the topological bulk property not only determines its fractionalized edge states but also the quantum criticality associated with the topological phase, where the elementary excitations are precisely those fractionalized edge degrees of freedom confined in the bulk of the topological phase.
Show less  Date Issued
 20160315
 Identifier
 FSU_libsubv1_wos_000372409100002, 10.1103/PhysRevB.93.115125
 Format
 Citation
 Title
 Transport evidence for the threedimensional Dirac semimetal phase in ZrTe5.
 Creator
 Zheng, Guolin, Lu, Jianwei, Zhu, Xiangde, Ning, Wei, Han, Yuyan, Zhang, Hongwei, Zhang, Jinglei, Xi, Chuanying, Yang, Jiyong, Du, Haifeng, Yang, Kun, Zhang, Yuheng, Tian, Mingliang
 Abstract/Description

Topological Dirac semimetal is a newly discovered class of materials which has attracted intense attention. This material can be viewed as a threedimensional (3D) analog of graphene and has linear energy dispersion in bulk, leading to a range of exotic transport properties. Here we report direct quantum transport evidence of the 3D Dirac semimetal phase of layered material ZrTe5 by angulardependent magnetoresistance measurements under high magnetic fields up to 31 T. We observed very clear...
Show moreTopological Dirac semimetal is a newly discovered class of materials which has attracted intense attention. This material can be viewed as a threedimensional (3D) analog of graphene and has linear energy dispersion in bulk, leading to a range of exotic transport properties. Here we report direct quantum transport evidence of the 3D Dirac semimetal phase of layered material ZrTe5 by angulardependent magnetoresistance measurements under high magnetic fields up to 31 T. We observed very clear negative longitudinal magnetoresistance induced by chiral anomaly under the condition of the magnetic field aligned only along the current direction. Pronounced Shubnikovde Hass (SdH) quantum oscillations in both longitudinal magnetoresistance and transverse Hall resistance were observed, revealing anisotropic light cyclotron masses and high mobility of the system. In particular, a nontrivial piBerry phase in the SdH oscillations gives clear evidence for the 3D Dirac semimetal phase. Furthermore, we observed clear Landau level splitting under high magnetic field, suggesting possible splitting of the Dirac point into Weyl points due to broken timereversal symmetry. Our results indicate that ZrTe5 is an ideal platform to study 3D massless Dirac and Weyl fermions in a layered compound.
Show less  Date Issued
 20160309
 Identifier
 FSU_libsubv1_wos_000371734800006, 10.1103/PhysRevB.93.115414
 Format
 Citation
 Title
 Fermi surface reconstruction in FeSe under high pressure.
 Creator
 Terashima, Taichi, Kikugawa, Naoki, Kiswandhi, Andhika, Graf, David, Choi, EunSang, 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
 Abstract/Description

We report Shubnikovde 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 pressureinduced 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 Shubnikovde 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 pressureinduced 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)/EF similar to 0.1 even at P = 16.1 kbar.
Show less  Date Issued
 20160303
 Identifier
 FSU_libsubv1_wos_000371401700003, 10.1103/PhysRevB.93.094505
 Format
 Citation
 Title
 Magnetoinfrared spectroscopic study of thin Bi2Te3 single crystals.
 Creator
 Tung, L.C., Yu, W., CaddenZimansky, P., Miotkowski, I., Chen, Y. P., Smirnov, D., Jiang, Z.
 Abstract/Description

Thin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stackedslab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/ 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following...
Show moreThin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stackedslab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/ 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following ways: (1) Fieldinduced transfer of the optical weight from the lowerfrequency regime (< 250 cm(1)) to the higherfrequency regime (> 250 cm(1)) due to the redistribution of charge carriers across the Fermi surface. (2) Evolving of a Fanoresonancelike spectral feature from an antiresonance to a resonance with increasing magnetic field. Such behavior can be attributed to the electronphonon interactions between the Eu(1) optical phonon mode and the continuum of electronic transitions. (3) Cyclotron resonance resulting from the intervalence band Landau level transitions, which can be described by the electrodynamics of massive Dirac holes.
Show less  Date Issued
 20160229
 Identifier
 FSU_libsubv1_wos_000371398500002, 10.1103/PhysRevB.93.085140
 Format
 Citation
 Title
 WiedemannFranz law in the underdoped cuprate superconductor YBa2Cu3Oy.
 Creator
 Grissonnanche, G., Laliberte, F., DufourBeausejour, S., Matusiak, M., Badoux, S., Tafti, F. F., Michon, B., Riopel, A., CyrChoiniere, O., Baglo, J. C., Ramshaw, B. J., Liang, R., Bonn, D. A., Hardy, W. N., Kraemer, S., LeBoeuf, D., Graf, D., DoironLeyraud, N., Taillefer, Louis
 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 WiedemannFranz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortexmelting field Hvs. 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 WiedemannFranz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortexmelting field Hvs. 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 chargedensitywave order is known to exist. As the temperature is raised, the Lorenz ratio, Lxy = kappa(xy)/(sigma Txy), decreases rapidly, indicating that strong smallq scattering processes are involved.
Show less  Date Issued
 20160222
 Identifier
 FSU_libsubv1_wos_000370793000005, 10.1103/PhysRevB.93.064513
 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 offdiagonal 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 offdiagonal magnetoelectric tensor elements (forbidden by R (3) over bar symmetry) followed by a polarization flop accompanying the spin flop transition at mu H0(SF) = 6.5T. Mossbauer spectroscopy on MnTiO3 gently doped with Fe57 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 spinlattice coupling in the magnetoelectric properties of MnTiO3 is likely more important than previously thought.
Show less  Date Issued
 20160219
 Identifier
 FSU_libsubv1_wos_000370485900001, 10.1103/PhysRevB.93.054416
 Format
 Citation
 Title
 Superconducting transition temperature: Interacting Fermi gas and phonon mechanisms in the nonadiabatic regime.
 Creator
 Gor'kov, Lev P.
 Abstract/Description

We analyze the mathematical structure of equations for temperature TC of the superconductivity transition in a gas of interacting Fermi particles or at the phononmediated pairing in a metal in the case of nonadiabatic conditions omega(0) >= EF, i.e., when the characteristic phonon frequency omega(0) is comparable or larger than the Fermi energy EF. As the methods of calculating TC in common superconductors are not applicable in the nonadiabatic regime, the integral equations for TC are...
Show moreWe analyze the mathematical structure of equations for temperature TC of the superconductivity transition in a gas of interacting Fermi particles or at the phononmediated pairing in a metal in the case of nonadiabatic conditions omega(0) >= EF, i.e., when the characteristic phonon frequency omega(0) is comparable or larger than the Fermi energy EF. As the methods of calculating TC in common superconductors are not applicable in the nonadiabatic regime, the integral equations for TC are derived in the logarithmic approximation. The new equations contain no divergent terms in the antiadiabatic limit. The results can be immediately generalized to anisotropic band superconductors.
Show less  Date Issued
 20160217
 Identifier
 FSU_libsubv1_wos_000370244300002, 10.1103/PhysRevB.93.054517
 Format
 Citation
 Title
 Equilibrium, metastability, and hysteresis in a model spincrossover material with nearestneighbor antiferromagneticlike and longrange ferromagneticlike 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 spincrossovermaterialwith a twostep transition between the highspin and lowspin states. This model is a mapping onto a squarelattice S = 1/2 Ising model with antiferromagnetic nearestneighbor and ferromagnetic HusimiTemperley ( equivalentneighbor) longrange interactions. Phase diagrams obtained by the two methods for weak and strong longrange interactions...
Show morePhase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean field method for a simplified model of a spincrossovermaterialwith a twostep transition between the highspin and lowspin states. This model is a mapping onto a squarelattice S = 1/2 Ising model with antiferromagnetic nearestneighbor and ferromagnetic HusimiTemperley ( equivalentneighbor) longrange interactions. Phase diagrams obtained by the two methods for weak and strong longrange interactions are found to be similar. However, for intermediatestrength longrange interactions, the Monte Carlo simulations show that tricritical points decompose into pairs of critical end points and meanfield critical points surrounded by hornshaped regions of metastability. Hysteresis loops along paths traversing the horn regions are strongly reminiscent of thermal twostep transition loops with hysteresis, recently observed experimentally in several spincrossover materials. We believe analogous phenomena should be observable in experiments and simulations for many systems that exhibit competition between local antiferromagneticlike interactions and longrange ferromagneticlike interactions caused by elastic distortions.
Show less  Date Issued
 20160216
 Identifier
 FSU_libsubv1_wos_000370244600002, 10.1103/PhysRevB.93.064109
 Format
 Citation
 Title
 Peculiarities of superconductivity in the singlelayer FeSe/SrTiO3 interface.
 Creator
 Gor'kov, Lev P.
 Abstract/Description

Observation of replica bands in the angleresolved photoemission spectroscopy (ARPES) spectra of singlelayer FeSe on a strontium titanate substrate revealed a phonon component contribution to mechanisms behind its highTc superconductivity. We study the interaction of the inlayer FeSe electrons with the electric potential of the longitudinal (LO) modes at the surface of bulk SrTiO3. A twodimensional system of charges at the FeSe/SrTiO3 interface includes both the itinerant and the...
Show moreObservation of replica bands in the angleresolved photoemission spectroscopy (ARPES) spectra of singlelayer FeSe on a strontium titanate substrate revealed a phonon component contribution to mechanisms behind its highTc superconductivity. We study the interaction of the inlayer FeSe electrons with the electric potential of the longitudinal (LO) modes at the surface of bulk SrTiO3. A twodimensional 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 electronLOphonon interaction. In what follows, the dielectric constant serves as a free parameter and is determined using the ARPES measurements of the replicas. Twodimensional Coulomb screening is accounted for in the randomphase 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 LOphononmediated pairing alone cannot account for the temperatures of the superconducting transitions Tc in the singlelayer FeSe/SrTiO3 reported in these experiments. This does not exclude that the LOphonon mechanisms can become more significant in differently and better prepared singlelayer FeSe films. Available experiments are briefly discussed. Thus far no measurements exist on the dependence of Tc on the concentration of electrons doped into the inlayer FeSe band.
Show less  Date Issued
 20160212
 Identifier
 FSU_libsubv1_wos_000370021500003, 10.1103/PhysRevB.93.060507
 Format
 Citation