Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session F56: Cuprate and Iron Superconductor Normal State Properties |
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Sponsoring Units: DCMP Chair: Ming Yi, Rice Univ Room: Mile High Ballroom 2C |
Tuesday, March 3, 2020 8:00AM - 8:12AM |
F56.00001: Fermi surface transformation across the pseudogap critical point in the cuprate Nd-LSCO from thermoelectric measurements Adrien Gourgout, Clement Collignon, Amirreza Ataei, Sven Badoux, Gael Grissonnanche, Marie-Eve Boulanger, Francis Laliberte, Jianshi Zhou, Qianli Ma, Bruce D. Gaulin, Nicolas Doiron-Leyraud, Louis Taillefer In cuprate superconductors, the nature of the pseudogap phase and its interplay with superconductivity are still unclear. Its onset at a doping p* is characterized by a drop in the carrier density n from n = 1+p above p* to n = p below p* [1]. In Nd0.4La1.6-xSrxCuO4 (Nd-LSCO), this shows up as a low-temperature upturn in the resistivity ρ and Hall coefficient RH at dopings below p* = 0.23 [2]. Here we present a series of thermoelectric measurements in Nd-LSCO across p*, in magnetic fields large enough to suppress superconductivity. For a heat current in the CuO2 planes, the Seebeck coefficient S shows a large increase at low temperature below p*, confirming the loss of carrier density. Application of pressure suppresses the low-T upturn in S/T, as it did the upturn in ρ and RH [3]. For a heat current perpendicular to the CuO2 planes, we find that S is isotropic for p > p*, i.e. Sc/T and Sa/T are equal (and positive) in the T=0 limit. In sharp contrast, Sc becomes negative at low temperature when p < p*, revealing a profound change in the Fermi surface topology across p*. |
Tuesday, March 3, 2020 8:12AM - 8:24AM |
F56.00002: Spiral magnetic order in high-Tc cuprates - a ground state candidate at high magnetic fields Johannes Mitscherling, Pietro Maria Bonetti, Demetrio Vilardi, Walter Metzner The normal state beneath the superconducting dome determines the fluctuations that govern the anomalous properties of cuprate superconductors in a wide range of their phase diagram. Recent experiments at very high magnetic fields shed new light on the phenomenology of the high field ground state: A drastic change in the carrier density at the onset of the pseudogap observed in various cuprate compounds, thermodynamic signatures of a quantum critical point at this doping and, very recently, NMR and ultrasound experiments indicated glassy antiferromagnetic order up to the pseudogap onset. |
Tuesday, March 3, 2020 8:24AM - 8:36AM |
F56.00003: Thermodynamic evidence of quantum criticality at the pseudogap critical point of cuprate superconductors Clément Girod, Bastien Michon, Maude le Lizaire, Adrien Gourgout, Sven Badoux, Nicolas Doiron-Leyraud, Francis Laliberte, Jozeph Kačmarčík, Simon Verret, Jianshi Zhou, Qianli Ma, Mirela Dragomir, Hannah A. Dabkowska, Bruce D. Gaulin, Sunseng Pyon, Tomohiro Takayama, Hidenori Takagi, Guo-Qing Zheng, shimpei ono, Christophe Marcenat, Louis Taillefer, Thierry Klein The emergence of superconductivity in the vicinity of a magnetic quantum critical point (QCP) in heavy-fermion, iron-based, organic and electron-doped cuprate superconductors showcases the important relation between quantum criticality and pairing. In hole-doped cuprates, long-range antiferromagnetic order vanishes with doping well before superconductivity appears. Instead, it is around the critical doping p* where the enigmatic pseudogap phase ends that superconductivity exists. The fact that the electrical resistivity displays a linear temperature dependence at low temperature in all these systems, including hole-doped cuprates [1], is suggestive. Here we provide thermodynamic evidence of a QCP in hole-doped cuprates from low-temperature measurements of the specific heat in magnetic fields up to 35 T, high enough to suppress superconductivity. In LSCO, Eu-LSCO, Nd-LSCO and Bi2201, we observe an electronic specific heat that grows as C/T ~ log(1/T) at p ~ p* [2], the classic thermodynamic signature of quantum criticality. |
Tuesday, March 3, 2020 8:36AM - 8:48AM |
F56.00004: Large negative thermal Hall conductivity in cuprate Mott insulators Marie-Eve Boulanger, Gael Grissonnanche, Maxime Dion, Etienne Lefrancois, Ruixing Liang, Walter N Hardy, Douglas A Bonn, Jianshi Zhou, Louis Taillefer A large negative thermal Hall signal kxy has recently been observed to appear in the pseudogap phase of cuprates [1]. This signal persists to zero doping, in the antiferromagnetic Mott insulator La2CuO4. While it is clearly not due to electrons, this kxy signal could come from magnons, or phonons — or more exotic excitations. To shed light on the underlying mechanism, we measured kxy in two additional cuprate Mott insulators: Nd2CuO4 and Sr2CuO2Cl2 . We observe a large negative kxy signal in both materials. Because of the absence of spin canting in either of these materials without apical oxygens, and because of the absence of any change in kxy upon crossing different magnetic states in Nd2CuO4, we infer that magnons are not the heat carriers responsible for kxy. The similarity in the temperature dependence of kxy and kxx suggests a phonon scenario. If so, the mechanism whereby the pseudogap phase confers chirality to phonons remains to be elucidated. |
Tuesday, March 3, 2020 8:48AM - 9:00AM |
F56.00005: Deep in the electron-doped cuprate pseudogap regime: a two-particle self-consistent approach with GG0 approximation to the two-dimensional Hubbard model Yan Wang, Yuri Vilk, Andre-Marie Tremblay In cuprate high-Tc superconductors, the pseudogap (PG) manifests itself at low temperature as a gradual depletion of the density of states at the Fermi level. In electron-doped cuprates, the nonperturbative semianalytical two-particle-self-consistent (TPSC) approach naturally explains the PG as the finite-T precursor of the antiferromagnetic (AFM) bands of the ordered ground state at T=0. In contrast to Mott physics, the PG opens in two dimensions at hot spots in momentum space due to scattering off spin-fluctuations when the AFM correlation length becomes longer than the thermal de Broglie wavelength. However, TPSC eventually fails at temperatures deep in the PG regime with exponentially growing AFM correlation length. Here, we extend TPSC with the GG0 approximation to the irreducible particle-hole polarization where one of the propagators G is self-consistently dressed by TPSC self-energy. Benchmarking with other controlled numerical methods, we demonstrate that this modified TPSC approach predicts quite accurate one-particle and two-particle properties deep in the PG regime, satisfies various sum rules and consistency relations and joins smoothly with the T=0 AFM ground state. |
Tuesday, March 3, 2020 9:00AM - 9:12AM |
F56.00006: Disorder effects on the phase diagram of electron-doped cuprates using the two-particle self-consistent approach Chloe-Aminata Gauvin-Ndiaye, Andre-Marie Tremblay The two-particle self-consistent approach (TPSC) is a highly accurate theoretical method for electronic systems that can be described by the one-band Hubbard model in the weak to intermediate coupling regime. [1] In particular, it can successfully describe the electron-doped cuprates. One of the predictions of TPSC for these materials is that the pseudogap occurs when the antiferromagnetic spin correlation length become larger than the thermal de Broglie wave length. [1,2] This TPSC condition for the pseudogap has been confirmed experimentally in the underdoped regime. However, this analysis fails in the optimal doping regime. [3,4] In this work, we include the effect of impurities and disorder in TPSC using the impurity averaging technique. We then investigate the effect of disorder on the TPSC condition for the pseudogap and on the critical doping for the crossover temperature. |
Tuesday, March 3, 2020 9:12AM - 9:24AM |
F56.00007: Measured vs. Calculated Phonon Dispersions in the Cuprate HgBa2CuO4 Irada Ahmadova, Tyler Sterling, Aaron Sokolik, Adrian Merritt, Douglas L Abernathy, Mun K. Chan, Yang Tang, Guichuan Yu, Martin Greven, Dmitry Reznik Taking the prototypical high-Tc superconductor HgBa2CuO4 as an example, I will compare ab-initio density-functional-theory (DFT) calculations of the phonon dispersions to inelastic neutron scattering results that exhibit an anomaly in the Cu-O bond stretching branch. We have performed a series of calculations using several codes at different levels of approximation. Our results show good qualitative agreement for all codes, but only one gave a good quantitative agreement (better than 10%). All DFT calculations fail to reproduce the experimentally observed anomalous dispersion of the bond-stretching phonon branch. I will conclude my talk by mentioning other computational methods that may improve the agreement between the calculations and measurement. |
Tuesday, March 3, 2020 9:24AM - 9:36AM |
F56.00008: Nature of the pseudogap in cuprate superconductors Yoandris Vielza de la Cruz The base of the mean-field model that describes the main physical properties of the cuprate superconductors is presented, the single-band Hubbard Hamiltonian of the Mott-states of electrons on CuO-plane. In the present work, the Hamiltonian is diagonalized on a Hartree-Fock base of collinear spins states that leaves fixed the magnetic order on the square sublattices. Adjusted the mean-field in the unit cell to a gap of ~ 2 eV at half-filling and to a maximum value of pseudogap observed of ~ 100 meV, an evaluation of the Hartree-Fock Mott-states in doping with holes and electrons and at the zero absolute temperature is made. It is shown that the mean-field adjust the density of the states at the Fermi level according to the experimental measure. The base of the Hartree-Fock Mott-states prove that the opening of the pseudogap in cuprate superconductors define a phase of low density of states at the Fermi level resulting from Coulomb repulsion on Cu-sites that penalizes two electrons being close to each other. It is also argued that the spontaneous breaking of rotational symmetry in the antiferromagnetic order of the Mott-states leads to the electron pair formation in cuprate superconductors. |
Tuesday, March 3, 2020 9:36AM - 9:48AM |
F56.00009: Criticality vs material inhomogeneity: an analysis of LSCO magnetoresistance data Christian Boyd, Philip Phillips Recent thin-film LSCO measurements have observed, in addition to the hallmark T-linear resistivity of cuprates near optimal doping, B-linear resistivity in strong magnetic fields. We analyze existing data on this thin-film sample to demonstrate that, contrary to the high-Tc iron superconductors near optimal doping, no single scaling function of temperature and field can describe the magnetoresistance data across all measured temperatures above and below the superconducting Tc. We model the high-temperature data within a classically-disordered system of conducting patches with qualitative accuracy. Interestingly, the breakdown of this model at low temperatures when the mean free path exceeds the lengthscale of disorder happens to correspond with the experimentally observed region where the resitivity changes character to become simultaneously T,B linear. |
Tuesday, March 3, 2020 9:48AM - 10:00AM |
F56.00010: What can Density Functional Theory tell us about Pseudogaps? Robert Markiewicz, Yubo Zhang, Christopher Lane, James Furness, Matt Matzelle, Bernardo Barbiellini, John P. Perdew, Jianwei Sun, Arun Bansil We have shown recently that advanced exchange-correlation functionals can enable first-principles treatment of the electronic, geometric and magnetic structure of the cuprates and other correlated materials without the need to invoke ad hoc parameters such as the Hubbard U. [1,2] Here, we focus on how in this picture the pseudogap phase in YBaCu3O7 involves a large number of competing magnetic and stripe phases with small energy differences, which can be looked upon as simple antiferromagnets with topological defects, i.e. defects consisting of stacking faults and charged antiphase boundaries or the charged stripes[3,4]. A simple thermodynamic model suggests that the pseudogap consists of fluctuating short-range ordered (SRO) phases, while the strange metal corresponds to defect unbinding. The SRO phases display nematicity and Fermi arcs. Comparisons with experiment will be discussed. |
Tuesday, March 3, 2020 10:00AM - 10:12AM |
F56.00011: Determine the spatial locality of self-energy of LiFeAs Minjae Kim, Hu Miao, Gabriel Kotliar Understanding of the electronic correlations is crucial to explain the electronic properties, magnetism, and superconductivity of the iron-based superconductors (FeSCs). An important question is the degree of spatial locality of the electronic correlations. Local correlations is the starting point of dynamical mean-field theory (DMFT), which has been proved to be powerful in understanding spectroscopic properties of the FeSCs [1,2]. However, recent theoretical and experimental reports on one of the FeSCs, LiFeAs, suggested the importance of non local correlations[3,4]. In this presentation, we extract spatially resolved and orbital dependent electronic self-energy of LiFeAs from angle resolved photoemission spectroscopy with density functional theory as a reference frame, and discuss the level of locality in the different orbitals, with the xy orbital being more local than the xz yz. We also discuss how the level of non locality depends on energy. |
Tuesday, March 3, 2020 10:12AM - 10:24AM |
F56.00012: Quasiclassical theory of C4-symmetric magnetic order in disordered iron-based superconductors Maxim Dzero In some hole-doped iron-based superconductors the magnetic order emerges with underlying C4-symmetry. This magnetic order can be viewed as a state with two ordering vectors with the corresponding magnetizations M1 and M2. In my talk, I will formulate a quasi-classical theory of such a state. Specifically, I will consider a three-band model, which, apart from the magnetic interactions, includes intra- and interband disorder scattering potentials. I will develop the quasiclassical approach for such a model and show how disorder scattering rates enhance the emergence of the C4-symmetric magnetic order. |
Tuesday, March 3, 2020 10:24AM - 10:36AM |
F56.00013: Nematicity in the pseudogap and charge order phases of the cuprate YBCO Louis Taillefer, Gael Grissonnanche, Olivier Cyr-Choiniere, Nicolas Doiron-Leyraud, Ruixing Liang, Walter N Hardy, Douglas A Bonn Electronic nematicity is the spontaneous breaking of rotational symmetry in a metal, and it has been argued to potentially strengthen superconductivity. It is a key feature of iron-based high-temperature superconductors. In cuprate high-temperature superconductors, a number of experiments have revealed evidence of nematicity, but its origin remains unclear. We measured the in-plane anisotropy of the electrical resistivity ρ(T) and the Seebeck coefficient S(T) in a crystal of the cuprate YBa2Cu3Oy, at hole concentration p = 0.12. By using the same sample and contacts to measure transport along the a axis and the b axis of the orthorhombic crystal structure, by detwinning this sample twice, such that its length was first along a and then along b, we were able to precisely obtain the intrinsic in-plane anisotropy of these two longitudinal transport coefficients. We find no trace of any additional anisotropy in either ρ(T) or S(T) upon crossing below the pseudogap temperature T*. A large anisotropy appears only at much lower temperature, in tandem with the emergence of charge density wave correlations. We conclude that the pseudogap phase itself is not nematic, and the nematicity in YBa2Cu3Oy originates instead from the unidirectional charge order and its precursor correlations. |
Tuesday, March 3, 2020 10:36AM - 10:48AM |
F56.00014: Diverse unconventional density wave states in high-Tc cuprates and other unconventional superconductors Hiroshi Kontani, Kouki Kawaguchi, Rina Tazai, Youichi Yamakawa, Seiichiro Onari We discuss the mechanism of diverse nematic orders in various strongly correlated electron systems, by considering the interference among different fluctuations given by vertex corrections (VCs). We mainly focus on the ferro- and stripe-bond orders in cuprate superconductors and organic superconductor κ-(BEDT-TTF)2X. The bond order formation is closely related to the pseudogap phenomena in these systems. We also discuss important effects on bond-order fluctuations on the superconductivity and other electronic properties. We also discuss possible time-reversal-symmetry breaking nematic order based on the Hubbard model. |
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F56.00015: Investigation of the Orbital Moment on the Fe Impurities in Iron-Based Superconductor SHIYU PENG, JIANPENG LIU, Hongming Weng, Xi Dai Our previous study show that the orbital exchange process induced by large orbital magnetic moment can lead to quantum anomalous vortices, which may further support robust Majorana zero-energy modes together with the topologically nontrivial surface states. In the present study, by applying LDA+Gutzwiller method we have systematically studied the value of the orbital magnetic moment as the function of the height between the Fe impurity and the surface of superconducting Fe(Te,Se). The local Coulomb Interaction between the electrons on the Fe impurities has been treated carefully by the rotational invariant Gutzwiller method with the variational parameters corresponding to the the most generic situation. Our results show the orbital contribution to the magnetic moment is always sizeable in this system and can be strongly affected by the impurity height. |
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