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 ManyBody 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 metalliclike resistivity up to very high temperature, with values exceeding the MottIoffeRegel (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 longlived 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 SachdevYeKitaev 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 selfconsistency in DFT+DMFT calculations for complex transition metal oxides Alexander Hampel, Sophie Beck, Claude Ederer We investigate the effect of charge selfconsistency (CSC) in densityfunctional theory plus dynamical meanfield theory calculations compared to simpler “oneshot” 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 metalinsulator transition (MIT), for which the importance of CSC is currently not well understood. Specifically, we analyze the strainrelated orbital polarization in the correlated metal CaVO_{3} and the spontaneous electronic charge disproportionation in the rareearth nickelate LuNiO_{3}. In both cases, we find that the CSC treatment reduces the charge redistribution compared to cheaper oneshot calculations. However, while the MIT in CaVO_{3} 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 doublecounting correction in CSC calculations containing different inequivalent sites. 
Thursday, March 18, 2021 3:48PM  4:00PM Live 
V21.00003: eDMFT Study of Filled Skutterudite CeGe_{4}Pt_{12} at Finite Temperatures Khandker Quader, Gheorghe Pascut, Michael Widom, Kristjan Haule We present results of selfconsistent embeddeddynamical mean field theory (eDMFT) calculations on the rareearth filled skutterudite CeGe_{4}Pt_{12}, with felectron correlations, across a wide range of temperature. We were able to obtain converged eDMFT results down to T ~ 15 K. The calculated felectron selfenergy on the imaginary (Matsubara frequency) and real axis, density of states, hybridization, and spectral function collectively suggest the following picture: CurieWeiss behavior with fluctuating felectron moments for T > 200K; behavior consistent with Kondo lattice of partially compensated felectron moments for intermediate T ~ 25K – 100K; Nozierestype 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 LaNiO_{2} : an eDMFT perspective Khandker Quader, Gheorghe Pascut, Kristjan Haule Current interest in the nickelates, RNiO_{2} (R=La, Nd) stem from the discovery of superconductivity in hole doped infinitelayer NdNiO_{2}. To understand the underlying physics, we performed selfconsistent density functional theory with embedded dynamical mean field theory (eDMFT) calculations on LaNiO_{2}, simpler than NdNiO_{2}, nevertheless illuminating. Using the prototypical LaNiO_{2} crystal structure we propose a temperaturecorrelation phase diagram. Depending on relevant computed quantities, the system exhibits varied behavior: Fermi liquid (FL) versus nonFL and magnetic versus nonmagnetic CurieWeiss. Computing the correlation strength in LaNiO2 using constrained eDMFT, we found the compound to be nonmagnetic, which is consistent with neutron scattering experiments on RNiO_{2}. 
Thursday, March 18, 2021 4:12PM  4:24PM Live 
V21.00005: Origin of metalinsulator 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 metaltoinsulator 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) SrCoO_{3} is a FM metal and the oxygendeficient (ndoped) brownmillerite SrCoO_{2.5} 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 LaNiO_{3}, SrFeO_{3,} and SrCoO_{3} also undergo MIT when ndoped via hightolow valence compositional changes. We posit that the ABO_{3} PV's most prone to MIT are self holedoped negative charge transfer materials. Upon ndoping, ligand hole passivation at certain sites occurs, leading to a bonddisproportionated gapped state due to chargelattice 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 manybody interaction Suman Chatterjee, Sarthak Das, Takashi Taniguchi, Kenji Watanabe, Kausik Majumdar The lightmatter 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 manybody exciton complexes [12]. 
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 fielddependent contribution which is dominant in a parametrically large spatial interval. Moreover, in this interval, the fielddependent oscillations do not decay with distance. This effect originates from the magneticfieldinduced chiral symmetry breaking near the Dirac point and implies anomalous sensitivity of the interaction effects in graphene and graphenebased heterostructures to a weak nonquantizing magnetic field. 
Thursday, March 18, 2021 4:48PM  5:00PM Live 
V21.00008: Ab Initio ManyBody Treatment of Interlayer Excitons in Mg_{2}TiO_{4} Thin Films Stephen Eltinge, Kidae Shin, Sangjae Lee, Hyungki Shin, Juan Jiang, Hawoong Hong, Bruce Davidson, Ke Zou, Charles Ahn, Frederick Walker, Sohrab IsmailBeigi Twodimensional transition metal oxides (2DTMOs) are a promising addition to the growing array of functional 2D materials, with potential applications related to their longlived, 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 Waalsbonded 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 Mg_{2}TiO_{4}, whose low energy electronic states are dominated by Ti and O orbitals. We review the structure of these thin films and report on manybody calculations of their electronic excitations. We show density functional theory results on band alignment and the spatial locality of bandedge wavefunctions that demonstrate the viability of longlived 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 Mg_{2}TiO_{4}. 
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 meanfield theory (DMFT). Instead of using small impurities defined in a lowenergy 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 realfrequency axis, combined with a oneshot G_{0}W_{0} treatment of longrange interactions. We apply our full cell approach to bulk Si, two antiferromagnetic correlated insulators NiO and αFe_{2}O_{3}, and the paramagnetic correlated metal SrMoO_{3}, with impurities containing up to 10 atoms and 124 orbitals. We find that spectral properties, magnetic moments, and twoparticle 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 quantumHallmagnet junctions Nemin Wei, Chunli Huang, Allan MacDonald Motivated by recent nonlocal transport studies of quantumHallmagnet (QHM) states formed in monolayer graphene’s N = 0 Landau level (Wei et.al Science 362, 229233; Zhou et.al Nature Physics 16, 154–158(2020)), we study the scattering of QHM magnons by gatecontrolled junctions between states with different integer filling factors \nu. For the \nu = 1 − 11 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 = 101 geometry, we find that kinematic constraints completely block magnon transmission if the incident angle exceeds a critical value. Our results explain the suppressed nonlocalvoltage signals observed in the \nu = 101 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 spinspin correlations giving information about the longrange 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 realspace 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: Realtime 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 xray 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 realtime equationofmotion coupledcluster (RTEOMCC) method for the core spectral function where the Green's function is computed from the overlap <N1N1,t> between the initial coreexcited wavefunction and its timepropagated form. The timedependent 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 RTEOMCC to systems with hundreds of electrons. We also discuss extensions required to include correlations in the ground state. 
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