Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F54: PerovskitesFocus Live
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Sponsoring Units: DMP Chair: Jian Liu, University of Tennessee |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F54.00001: Monte Carlo simulation of a strong SOC model for d1 double perovskite Rong Cong, Vesna Mitrovic Recent NMR experiments revealed exotic quantum phases in the magnetic Mott insulator with strong spin-orbit coupling Ba2NaOsO6[1]. In an attempt to associate possible spin and orbital patterns with these NMR findings, we performed Monte Carlo simulations to study a microscopic model for d1 double perovskites magnetic Mott insulators with strong spin orbit coupling and multipolar spin interactions[2]. We obtained the low temperature phase diagram, involving both spin and orbital degree of freedoms, by magnetic annealing. We found that the zero temperature phase diagram consists of three phases (a fluctuating xyAFM, a canted FM[100], and a magnetic quadrupolar state), each with distinct corresponding orbital ordering patterns. The xyAFM and the quadrupolar state are also supported at intermediate temperatures by enhanced fluctuations at finite temperature. Furthermore, we reveal that the ground state evolves from canted FM[100] state to the quadrupolar state with increasing electric quadrupole-quadrupole interaction. A phase diagram as a function of the applied magnetic field will also be discussed. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F54.00002: Charge-transfer energy in iridates: A hard x-ray photoelectron spectroscopy study Daisuke Takegami, Deepa Kasinathan, Klaus K. Wolff, Simone Altendorf, Chun-Fu Chang, Katharina Hoefer, Anna Melendez-Sans, Yuki Utsumi, Federico Meneghin, Duy Ha, Chien-Han Yen, Kai Chen, Chang-Yang Kuo, Yen-Fa Liao, Ku-Ding Tsuei, Ryan Morrow, Sabine Wurmehl, Bernd Büchner, Beluvalli-Eshwarappa Prasad, Martin Jansen, Alexander Komarek, Philipp Hansmann, Liu Tjeng We have investigated the electronic structure of iridates in the double perovskite crystal structure containing either Ir4+ or Ir5+ using hard x-ray photoelectron spectroscopy. The experimental valence band spectra can be well reproduced using tight-binding calculations including only the Ir 5d, O 2p, and O 2s orbitals with parameters based on the downfolding of the density-functional band structure results. We found that, regardless of the A and B cations, the A2BIrO6 iridates have essentially zero O 2p to Ir 5d charge-transfer energies. Hence double perovskite iridates turn out to be extremely covalent systems with the consequence being that the magnetic exchange interactions become very long ranged, thereby hampering the materialization of the long-sought Kitaev physics. Nevertheless, it still would be possible to realize a spin-liquid system using the iridates with a proper tuning of the various competing exchange interactions. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F54.00003: Effects of charge doping a Mott insulator with strong spin-orbit coupling Erick Garcia, Paola Caterina Forino, Rong Cong, Phuong Tran, Anna Tassetti, Giuseppe Allodi, Arneil P Reyes, Pat Woodward, Samuele Sanna, Vesna Mitrovic The study of emergent novel quantum phases that result from the competing interactions of strong electron correlations and spin-orbit coupling (SOC) is of great current relevance. Double perovskites with 5d transition metal ions display comparable magnitudes of electron correlations, crystal field, and SOC, making them perfect candidate materials to study the consequences of such interactions. We used this class of materials to probe the effect of charge doping on a Mott insulator with strong spin-orbit entanglement. Specifically, in this talk, we present a comprehensive study of the electron-doped powder, double perovskite Ba2Na1-xCaxOsO6 through the Na/Ca partial substitution using nuclear magnetic resonance (NMR), muon spin relaxation (uSR), and superconducting quantum interference device (SQUID) measurements for 0 < x < 1. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F54.00004: Knight shift anisotropy as a function of charge doping in a Mott insulator with strong spin-orbit coupling Zhenxiang Gao, Rong Cong, Erick Garcia, Vesna Mitrovic We present a detailed analysis of NMR powder spectral patterns of the double perovskite Ba2Na1-xCaxOsO6 (0 < x < 1), a charge doped Mott insulator with strong spin-orbit coupling (SOC). The analysis of the spectra in the low temperature exotic quantum phases across the entire doping range reveals anisotropy in the local susceptibility. The physics implication on the nature of these low temperature phases will be discussed. |
Tuesday, March 16, 2021 12:18PM - 12:30PM Live |
F54.00005: First-principles study of the electronic, magnetic, and crystal structure of perovskite molybdates Jeremy Lee-Hand, Alexander Hampel, Cyrus Dreyer The molybdate oxides SrMoO3, PbMoO3, and LaMoO3 are a class of metallic perovskites that exhibit interesting properties including high mobility, and unusual resistivity behavior. We use first-principles methods based on density functional theory to explore the electronic, crystal, and magnetic structure of these materials. In order to account for the electron correlations in the partially-filled molybdenum 4d shell, a local Hubbard U interaction is included. The value of U is estimated using the constrained random-phase approximation (cRPA), and the dependence of the results on the choice of U are explored. For all materials, GGA + U predicts a metal with orthorhombic, antiferromagnetic structure for the cRPA value of U. The octohedral rotations for SrMoO3 and PbMoO3 are found to be overestimated compared to the experimental low-temperature structure. |
Tuesday, March 16, 2021 12:30PM - 12:42PM Live |
F54.00006: Electronic structure of epitaxially strained Sr2CrReO6 Guillaume Marcaud, Alex Lee, Adam Joseph Hauser, Fengyuan Yang, Sangjae Lee, Diego M Casa, Mary Upton, Thomas Gog, yilin Wang yilinwang@bnl.gov, Mark Dean mpmdean@gmail.com, Hua Zhou, Frederick Walker, Ignace Jarrige, Sohrab Ismail-Beigi, Charles Ahn Rhenium-based double perovskites (DP) possess rich physics, including magnetic ordering at room temperature, which is a result of an intricate interplay between physical and electronic structure. Among them, Sr2CrReO6 (SCRO) stands out due to a high Curie temperature of Tc=620K, a strain-tunable magnetocrystalline anisotropy, and an insulating ground state with a bandgap of 0.21 eV, which can be explained theoretically by orbital ordering. |
Tuesday, March 16, 2021 12:42PM - 1:18PM Live |
F54.00007: Iridium on the fcc lattice: new design principles for realizing Jeff = ½ moments and significant Kitaev interactions Invited Speaker: Adam Aczel Heavy transition metal magnets have been intensely investigated over the last decade due to their penchant for hosting a wide variety of exotic phases and phenomena. Of particular interest are systems with octahedrally-coordinated magnetic ions in a 5d5 electronic configuration, as the combination of large cubic crystal fields and strong spin-orbit coupling is expected to generate a Jeff = ½ electronic ground state that may be an essential ingredient for new classes of quantum spin liquids and superconductors. In this talk, I will discuss how spacing the iridium ions further apart and incorporating anions with low electronegativities into the crystal structure are useful design criteria for achieving unprecedented proximity to the ideal Jeff = ½ limit. One or both conditions are realized in the double perovskite iridate and iridium halide families, which have the general chemical formulas A2BIrO6 and A2IrX6 respectively. Notably, both structure types consist of a magnetic face-centered-cubic (fcc) sublattice, where nearest neighbor Kitaev interactions are symmetry-allowed through extended superexchange pathways. Therefore, I will also discuss the possibility of realizing significant Kitaev interactions in these families and their impact on the collective magnetic properties. Finally, I will explain how systems with Jeff = ½ moments on the fcc lattice can host exotic states of matter. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Live |
F54.00008: BCS-BEC crossover in a (t2g)4 excitonic magnet Nitin Kaushal, Rahul Soni, Alberto Nocera, Gonzalo Alvarez, Elbio Dagotto In the last few years, the spin-orbit-induced excitonic condensation in multiorbital electronic systems has attracted considerable attention [1-3]. We provide the full λ (spin-orbit coupling) versus Coulomb correlation (U) phase diagrams for both one- and two-dimensional lattices calculated using density matrix renormalization group and Hartree-Fock approximation, respectively [4]. We show that at large and intermediate U regimes, the spin-orbit exciton condensation is possible leading to staggered magnetic order. We show for the first time, the presence of (Bardeen-Cooper-Schrieffer) BCS to BEC crossover in the spin-orbit excitonic condensate. The canonical electron-hole excitations (excitons) transform into local triplon excitations at large U. We also found that at intermediate Hubbard U, increasing λ at fixed U the system transitions from an incommensurate spin-density-wave metal to a BCS excitonic insulator. Further increasing λ, the system eventually crosses over to the BEC limit. |
Tuesday, March 16, 2021 1:30PM - 1:42PM Live |
F54.00009: Phase coexistence and negative thermal expansion in the triple perovskite iridate Ba3CoIr2O9 Charu Garg, Deepak Kumar Roy, Martin Lonsky, Pascal Manuel, Antonio Cervellino, Jens Müller, Mukul Kabir, Sunil Nair The competing crystal field splitting, spin-orbit coupling, on-site Coulomb interaction, and Hund’s coupling lead to many novel electronic and magnetic states in the 5d transition metal based oxides, otherwise expected to be relatively simple metals (Annu. Rev. Condens. Matter Phys. 7, 195 (2016)). We present a hitherto unreported Ba3CoIr2O9, stabilizing in the hexagonal P63/mmc symmetry at 300K, it exhibits a magneto-structural transition to a monoclinic C2/c phase at 107 K – the highest known amongst all the triple perovskite iridates. Below 70 K, a part of the system transforms to a monoclinic phase with even lower symmetry (P2/c), and both these phases coexist down to the lowest measured temperatures. We observe a negative thermal expansion in this phase co-existence regime, driven by magnetic exchange striction, and is of relevance to a number of systems with pronounced spin-orbit interactions. Both theory and experiments indicate that the Ir5+ carries a finite magnetic moment, suggesting that the putative J = 0 state is avoided. Heat capacity, electrical resistance noise and dielectric susceptibility all point towards the stabilization of a highly correlated ground state in this system. |
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