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 V21: Precision Many-Body Physics VI: Real MaterialsFocus Live
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Sponsoring Units: DCOMP DCMP DAMOP Chair: Olga Goulko, University of Massachusetts Boston |
Thursday, March 18, 2021 3:00PM - 3:36PM Live |
V21.00001: Bad Metals and Planckian Metals: DMFT, SYK and physical realisations Invited Speaker: Antoine Georges Many materials with strong electronic correlations display metallic-like resistivity up to very high temperature, with values exceeding the Mott-Ioffe-Regel (MIR) criterion (`bad metals'). Understanding transport in this regime, in relation to spectroscopic probes such as optical conductivity and ARPES, raises the fundamental question of transport in regimes where long-lived quasiparticles may not exist. Recently, cold atomic gases in optical lattices have offered a beautiful experimental platform to investigate this question without the intervening effect of phonons. Even more challenging is the crossover into a `strange metal' regime at lower temperatures, in which resistivity becomes smaller than the MIR value and the scattering rate obey Planckian behavior with linear dependence on temperature. I will review recent work on these questions in the context of Dynamical Mean Field Theory and Sachdev-Ye-Kitaev models, as well as other analytical and computational approaches, assessing what is established at this point and which questions are still open. |
Thursday, March 18, 2021 3:36PM - 3:48PM Live |
V21.00002: Effect of charge self-consistency in DFT+DMFT calculations for complex transition metal oxides Alexander Hampel, Sophie Beck, Claude Ederer We investigate the effect of charge self-consistency (CSC) in density-functional theory plus dynamical mean-field theory calculations compared to simpler “one-shot” calculations for materials where interaction effects lead to a strong redistribution of electronic charges between different orbitals or between different sites. We focus on two systems close to a metal-insulator transition (MIT), for which the importance of CSC is currently not well understood. Specifically, we analyze the strain-related orbital polarization in the correlated metal CaVO3 and the spontaneous electronic charge disproportionation in the rare-earth nickelate LuNiO3. In both cases, we find that the CSC treatment reduces the charge redistribution compared to cheaper one-shot calculations. However, while the MIT in CaVO3 is only slightly shifted due to the reduced orbital polarization, the effect of the site polarization on the MIT in LuNiO3 is more subtle. Furthermore, we highlight the role of the double-counting correction in CSC calculations containing different inequivalent sites. |
Thursday, March 18, 2021 3:48PM - 4:00PM Live |
V21.00003: e-DMFT Study of Filled Skutterudite CeGe4Pt12 at Finite Temperatures Khandker Quader, Gheorghe Pascut, Michael Widom, Kristjan Haule We present results of self-consistent embedded-dynamical mean field theory (e-DMFT) calculations on the rare-earth filled skutterudite CeGe4Pt12, with f-electron correlations, across a wide range of temperature. We were able to obtain converged e-DMFT results down to T ~ 15 K. The calculated f-electron self-energy on the imaginary (Matsubara frequency) and real axis, density of states, hybridization, and spectral function collectively suggest the following picture: Curie-Weiss behavior with fluctuating f-electron moments for T > 200K; behavior consistent with Kondo lattice of partially compensated f-electron moments for intermediate T ~ 25K – 100K; Nozieres-type Fermi liquid behavior of the Kondo impurity model for low T ~ 15K and below - a very low Fermi liquid scale. Our results may provide plausible explanation of experimental trends at finite temperatures. |
Thursday, March 18, 2021 4:00PM - 4:12PM Live |
V21.00004: Temperature - Correlation Phase Diagram for LaNiO2 : an eDMFT perspective Khandker Quader, Gheorghe Pascut, Kristjan Haule Current interest in the nickelates, RNiO2 (R=La, Nd) stem from the discovery of superconductivity in hole doped infinite-layer NdNiO2. To understand the underlying physics, we performed self-consistent density functional theory with embedded dynamical mean field theory (eDMFT) calculations on LaNiO2, simpler than NdNiO2, nevertheless illuminating. Using the prototypical LaNiO2 crystal structure we propose a temperature-correlation phase diagram. Depending on relevant computed quantities, the system exhibits varied behavior: Fermi liquid (FL) versus non-FL and magnetic versus non-magnetic Curie-Weiss. Computing the correlation strength in LaNiO2 using constrained eDMFT, we found the compound to be non-magnetic, which is consistent with neutron scattering experiments on RNiO2. |
Thursday, March 18, 2021 4:12PM - 4:24PM Live |
V21.00005: Origin of metal-insulator transitions in correlated perovskites – a combined DFT+U and QMC investigation Michael Bennett, Guoxiang Hu, Guangming Wang, Olle Heinonen, Paul Kent, Jaron Krogel, Panchapakesan Ganesh The mechanisms that drive metal-to-insulator transitions (MIT) in correlated solids are not fully understood, though intricate couplings of charge, spin, orbital, and lattice degrees of freedom have been implicated. For example, the perovskite (PV) SrCoO3 is a FM metal and the oxygen-deficient (n-doped) brownmillerite SrCoO2.5 is an AFM insulator. Given the magnetic and structural transitions that accompany the MIT, the driving force for the transition is unclear. Interestingly, the PV metals LaNiO3, SrFeO3, and SrCoO3 also undergo MIT when n-doped via high-to-low valence compositional changes. We posit that the ABO3 PV's most prone to MIT are self hole-doped negative charge transfer materials. Upon n-doping, ligand hole passivation at certain sites occurs, leading to a bond-disproportionated gapped state due to charge-lattice coupling. Other orderings (magnetic, charge, orbital etc.) are secondary and may assist gap openings at small dopings. We use DFT methods along with explicitly correlated diffusion Monte Carlo to test these hypotheses and compare to experiments where possible. |
Thursday, March 18, 2021 4:24PM - 4:36PM Live |
V21.00006: Probing charged biexciton through controlled many-body interaction Suman Chatterjee, Sarthak Das, Takashi Taniguchi, Kenji Watanabe, Kausik Majumdar The light-matter interaction of monolayer transition metal dichalcogenides is dominated by excitons and the high binding energy of these makes TMDC monolayers an ideal platform for the exploration of many-body exciton complexes [1-2]. |
Thursday, March 18, 2021 4:36PM - 4:48PM Live |
V21.00007: Persistent Friedel oscillations in Graphene due to a weak magnetic field Ke Wang, Mikhail E. Raikh, Tigran Sedrakyan Two opposite chiralities of Dirac electrons in a 2D graphene sheet modify strongly the Friedel oscillations: electrostatic potential around an impurity in graphene decays much faster than in 2D electron gas. Here we show that a weak uniform magnetic field affects the Friedel oscillations in an anomalous way. It creates a field-dependent contribution which is dominant in a parametrically large spatial interval. Moreover, in this interval, the field-dependent oscillations do not decay with distance. This effect originates from the magnetic-field-induced chiral symmetry breaking near the Dirac point and implies anomalous sensitivity of the interaction effects in graphene and graphene-based heterostructures to a weak non-quantizing magnetic field. |
Thursday, March 18, 2021 4:48PM - 5:00PM Live |
V21.00008: Ab Initio Many-Body Treatment of Interlayer Excitons in Mg2TiO4 Thin Films Stephen Eltinge, Kidae Shin, Sangjae Lee, Hyungki Shin, Juan Jiang, Hawoong Hong, Bruce Davidson, Ke Zou, Charles Ahn, Frederick Walker, Sohrab Ismail-Beigi Two-dimensional transition metal oxides (2DTMOs) are a promising addition to the growing array of functional 2D materials, with potential applications related to their long-lived, strongly bound excitons. 2DTMOs are expected to be unusually stable since they do not react with water or oxygen species. However, unlike many other 2D materials, 2DTMOs do not naturally occur in stackable van der Waals-bonded layers, so they present challenges for structural prediction and characterization. Recent experimental work on the MgO(001) surface has demonstrated the growth of thin films of Mg2TiO4, whose low energy electronic states are dominated by Ti and O orbitals. We review the structure of these thin films and report on many-body calculations of their electronic excitations. We show density functional theory results on band alignment and the spatial locality of band-edge wavefunctions that demonstrate the viability of long-lived interlayer excitons, and that those results are preserved upon the consideration of electronic correlations. We also report on the quasiparticle properties, absorption spectrum, and excitonic binding energy of bulk Mg2TiO4. |
Thursday, March 18, 2021 5:00PM - 5:12PM Live |
V21.00009: Ab Initio Full Cell GW+DMFT for Correlated Materials Tianyu Zhu, Garnet Chan Quantitative prediction of electronic properties in correlated materials requires simulations without empirical truncations and parameters. We present a method to achieve this goal through a new ab initio formulation of dynamical mean-field theory (DMFT). Instead of using small impurities defined in a low-energy subspace, which require complicated downfolded interactions which are often approximated, we describe a full cell GW+DMFT approach, where the impurities comprise all atoms in a unit cell or supercell of the crystal. Our formulation results in large impurity problems, which we treat here with efficient quantum chemistry impurity solvers that work on the real-frequency axis, combined with a one-shot G0W0 treatment of long-range interactions. We apply our full cell approach to bulk Si, two antiferromagnetic correlated insulators NiO and α-Fe2O3, and the paramagnetic correlated metal SrMoO3, with impurities containing up to 10 atoms and 124 orbitals. We find that spectral properties, magnetic moments, and two-particle spin correlation functions are obtained in good agreement with experiment. |
Thursday, March 18, 2021 5:12PM - 5:24PM Live |
V21.00010: Spectral properties of the interacting homogeneous electron gas from algorithmic inversion Tommaso Chiarotti, Nicola Marzari, Andrea Ferretti Despite its simplicity, the interacting homogeneous electron gas is a paradigmatic test case in the study of the electronic structure of condensed matter. Beside being a model for valence electrons in simple metals, it also provides the fundamental ingredients for |
Thursday, March 18, 2021 5:24PM - 5:36PM Live |
V21.00011: Scattering of magnons at graphene quantum-Hall-magnet junctions Nemin Wei, Chunli Huang, Allan MacDonald Motivated by recent non-local transport studies of quantum-Hall-magnet (QHM) states formed in monolayer graphene’s N = 0 Landau level (Wei et.al Science 362, 229-233; Zhou et.al Nature Physics 16, 154–158(2020)), we study the scattering of QHM magnons by gate-controlled junctions between states with different integer filling factors \nu. For the \nu = 1| − 1|1 geometry we find magnons are weakly scattered by electric potential variation in the junction region, and that the scattering is chiral when the junction lacks a mirror symmetry. For the \nu = 1|0|1 geometry, we find that kinematic constraints completely block magnon transmission if the incident angle exceeds a critical value. Our results explain the suppressed non-local-voltage signals observed in the \nu = 1|0|1 case. |
Thursday, March 18, 2021 5:36PM - 5:48PM Not Participating |
V21.00012: A comparison of computed and experimental neutron diffraction intensity at large momentum for MnO and NiO Alexander Munoz, Lazar Kish, Kannan Lu, Thomas W Heitmann, Greg MacDougall, Lucas Wagner Magnetic neutron scattering measures spin-spin correlations giving information about the long-range spin order as well as the shape of the spin density in magnetic materials. Similarly, detailed first principles calculations directly compute the spin density in materials. In this talk, I will show our careful comparison between experimentally measured magnetic neutron intensities and three levels of ab initio theory: density functional theory in two approximations, and diffusion Monte Carlo. While each theory performs similarly for the simple antiferromagnet MnO, there are significant differences between density functional theory and diffusion Monte Carlo in NiO. In each case, we show that diffusion Monte Carlo reduces the error with respect to the experiment. By connecting the intensities to the real-space spin density, we show that diffusion Monte Carlo reduces the error by spreading the spin density away from the core of the transition metal sites. |
Thursday, March 18, 2021 5:48PM - 6:00PM Live |
V21.00013: Real-time Equation of Motion Coupled Cluster Green's Function Approach for Satellite Peaks in XPS Fernando Vila, John Rehr, Karol Kowalski, Bo Peng Satellite peaks in x-ray photoemission spectra arise from many body excitations that have heretofore been difficult to simulate from first principles. To address this problem we have developed (F. D. Vila et al., J. Chem. Theory Comput. doi:10.1021/acs.jctc.0c00639) a real-time equation-of-motion coupled-cluster (RT-EOM-CC) method for the core spectral function where the Green's function is computed from the overlap <N-1|N-1,t> between the initial core-excited wavefunction and its time-propagated form. The time-dependent CC amplitudes are obtained from coupled, first order, nonlinear differential equations using a CC singles ansatz. Here we present a new, efficient extension of the approach to CC doubles implemented in NWChem, where code for each matrix element is generated with the Tensor Contraction Engine. We present results showing that this implementation extends the applicability of RT-EOM-CC to systems with hundreds of electrons. We also discuss extensions required to include correlations in the ground state. |
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