Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Z55: Correlated Electron Materials IV |
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Sponsoring Units: GMAG Chair: Yiqing Hao, Oak Ridge National Laboratory Room: Room 305 |
Friday, March 10, 2023 11:30AM - 11:42AM |
Z55.00001: A systematic DFT+U and Quantum Monte Carlo benchmark of magnetic two-dimensional (2D) CrX3 (X = I, Br, Cl, F) Daniel Wines, Kamal Choudhary, Francesca Tavazza The search for two-dimensional (2D) magnetic materials has attracted a great deal of attention because of the experimental synthesis of 2D CrI3, which has a measured Curie temperature of 45 K. Often times, these monolayers have a higher degree of electron correlation and require more sophisticated methods beyond density functional theory (DFT). Diffusion Monte Carlo (DMC) is a correlated electronic structure method that has been demonstrated successful for calculating the electronic and magnetic properties of a wide variety of 2D and bulk systems, since it has a weaker dependence on the Hubbard parameter (U) and density functional. In this study we designed a workflow that combines DFT+U and DMC in order to treat 2D correlated magnetic systems. We chose monolayer CrX3 (X = I, Br, Cl, F), with a stronger focus on CrI3 and CrBr3, as a case study due to the fact that they have been experimentally realized and have a finite critical temperature. With this DFT+U and DMC workflow and the analytical method of Torelli and Olsen, we estimated an upper bound of 43.56 K for the Tc of CrI3 and 20.78 K for the Tc of CrBr3, in addition to analyzing the spin densities and magnetic properties with DMC and DFT+U. We expect that running this workflow for a well-known material class will aid in the future discovery and characterization of lesser known and more complex correlated 2D magnetic materials. |
Friday, March 10, 2023 11:42AM - 11:54AM |
Z55.00002: Correlated Metallic Phases in the Hubbard-Holstein Hamiltonians David K Campbell, Nahom Yirga, Ka-Ming Tam The one-dimensional Hubbard-Holstein Hamiltonian is rich with phases, with competition between the Hubbard interaction and the density coupling to the Holstein phonon driving a novel correlated metallic phase (the Luther-Emery liquid). We utilize the functional Renormalization Group (fRG) to explore the behavior of the metallic phase in two and three dimensional variants of the model. We construct the flow of both the electron-electron and electron-phonon vertices, with the latter enabling the calculation of phonon softening, the broadening of phonon linewidths, and the onset of charge order. We find a shrunken metallic phase in the three-dimensional model with rich superconducting correlations which show senstivity to the frequency of the Holstein phonon. Finally, we constuct a preliminary phase diagrams of the three-dimensional Hubbard-Holstein model. |
Friday, March 10, 2023 11:54AM - 12:06PM Author not Attending |
Z55.00003: Acoustic phonon instabilities in Fe1.06Te studied by inelastic neutron scattering Guratinder Kaur, Chris Stock, Edmond Chan, Efrain E Rodriguez The advent of superconductivity in iron pnictides and the iron chalcogenides family of compounds has triggered an active stream of novel 2D materials [1]. Specifically, this field intends to investigate the high Tc superconductors by tuning parameters such as chemical doping or external pressure [2,3]. The uniqueness of Fe-based superconductors lies in the layered crystal structure where magnetic iron ions reside in a tetrahedral coordination at room temperature. Here, we present inelastic neutron scattering results of Fe1+xTe which is isostructural to Fe (Se,Te) family of superconducting compounds. Fe1+xTe is composed of edge-sharing FeTe4 tetrahedra held by weak van der Waals interactions and the concentration of interstitial Fe2+ ion plays a crucial role in tuning the magnetic properties [2]. Below the Neel temperature of 75 K, it undergoes a structural phase transition from tetragonal (P4/nmm) to monoclinic (P21/m) symmetry [3]. We examine the acoustic phonon instabilities associated with this transition and compare with the results of pnictide materials. |
Friday, March 10, 2023 12:06PM - 12:18PM |
Z55.00004: Theoretical study of resonant inelastic x-ray scattering spectra of nickelates Umesh Kumar, Gabriel Kotliar Nickelates have become an important system to explore with the recent discovery of superconductivity in the infinite layer system. Here, we study and explore the multi-orbital Hubbard-Kanamori model that was recently reported in [Phys Rev X 12 011055 (2022)] and is relevant for nickelates. We evaluate the resonant inelastic x-ray scattering (RIXS) response for this model and explore the sensitivities of different parameters within the model. In this work, we reveal the signatures of tetragonal distortions in the RIXS spectra at the oxygen K-edge of nickelates. We further report the low-energy excitations in RIXS spectra sensitivity to Hund's coupling and its implications on the ground state of the system. Our work, therefore, shows that the low-energy excitations in the RIXS spectra, if further resolved, can put strong constraints on the model and highlight the relevant degrees of freedom in the nickelates. |
Friday, March 10, 2023 12:18PM - 12:30PM |
Z55.00005: Gapped boundary theory of 3d topological orders Zhu-Xi Luo Gapped boundaries of 2d nonchiral topological orders are well-understood and characterized by Lagrangian subalgebras. We extend the study to 3d and show that there exists a wide variety of options for gapped boundaries even in the simplest bosonic and fermionic toric code models. These boundaries can be organized into two classes corresponding to whether the flux string can end at the boundary. We illustrate the boundary theories from various perspectives including coupled layer construction, Walker-Wang model and field theory. Our results can be naturally generalized to other 3d topological orders. |
Friday, March 10, 2023 12:30PM - 12:42PM |
Z55.00006: Temperature Depedence of Spin and Charge Orders in the Doped Two-Dimensional Hubbard Model Bo Xiao, Yuan-Yao He, Antoine Georges, Shiwei Zhang Competing and intertwined orders including inhomogeneous patterns of spin and charge are observed in many correlated electron materials, such as high-temperature superconductors. Introducing a new development of the constrained-path auxiliary-field quantum Monte Carlo (AFQMC) method, we study the interplay between thermal and quantum fluctuations in the two-dimensional Hubbard model. We obtain an accurate and systematic characterization of the evolution of the spin and charge correlations as a function of temperature T and how it connects to the ground state, at three representative doping levels δ=1/5, 1/8, and 1/10. We find increasing short-range commensurate antiferromagnetic correlations as T is lowered. As the correlation length grows sufficiently large, a modulated spin-density-wave (SDW) appears. At δ=1/5, the SDW saturates and remains short-ranged as T→0. In contrast, at δ=1/8 and 1/10 this evolves into a ground-state stripe phase. We study the relation between spin and charge orders and find that formation of charge order appears to be driven by that of the spin order. We identify a finite-temperature phase transition below which charge ordering sets in and discuss the implications of our results for the nature of this transition. Furthermore, we study effects of a nonzero next-nearest-neighbor hopping t' on the nature of spin and charge correlations. |
Friday, March 10, 2023 12:42PM - 12:54PM |
Z55.00007: Superconducting Response in Extended Hubbard models with π-flux Hopping Nahom Yirga, David K Campbell, Shan-Wen Tsai Decomposed functional renormalization group (fRG) flows allow the efficient treatment of ordering in systems with broken translational symmetry. We extend these flows into the symmetry broken regime and utilize them to study superconducting responses in the Hubbard model on the checkerboard lattice. For the models considered, the fRG allows the estimation of the order parameter up to the moderate coupling regime and shows enhancement of superconducting correlations over those calculated for Extended Hubbard interactions on the square lattice. We use the fRG to construct a preliminary phase diagram of the Hubbard model on the checkerboard lattice as a function of doping. We then catalog the sensitivity of the system response to the number of singular modes retained in the decoupling and the initial value of the symmetry breaking term for the general case of repulsive interactions on a lattice with an arbitrary flux per unit cell. |
Friday, March 10, 2023 12:54PM - 1:06PM |
Z55.00008: Broken-symmetry fully self-consistent GW: analysis of spin contamination, extraction of effective magnetic Hamiltonians, and evaluation of Neel temperatures in solid antiferromagnets Pavel Pokhilko, Dominika Zgid Recently, we applied the thermodynamic Hellmann-Feynman theorem to fully self-consistent Green's function methods, derived two-particle density matrices for molecules, and analyzed electronic structure in terms of two-particle correlators. In this work, we extend this development to solids. Since the conventional measure of spin contamination based on 2> is not extensive, we propose two new extensive quantities, u> and uk=0>, that are suitable for measuring spin contamination in solids. We show that unlike previous DFT estimates, the unrestricted GW in NiO and MnO is close to the ideal ferromagnetic and broken-symmetry solutions, making extraction of effective magnetic couplings simple and unambiguous, agreeing well with very few quantitative finite-cluster wave-function calculations for NiO. The constructed effective Hamiltonian Heff can be extrapolated for the strongly correlated states and system sizes that cannot be easily captured by conventional calculations. For the description of macroscopic phenomena, such as phase transitions, a direct diagonalization of the extrapolated Heff is not feasible. Instead, we apply a high-temperature expansion for the magnetic susceptibility and heat capacity to this extrapolated Hamiltonian. The radius of convergence of the obtained series determines the Neel temperature TN. We show that the experimentally observed trend in Neel temperatures in transition metal compounds is reproduced by broken-symmetry self-consistent GW. |
Friday, March 10, 2023 1:06PM - 1:18PM |
Z55.00009: Dynamic mass generation on two-dimensional correlated quantum hyperbolic fluids Noble Gluscevich, Bitan Roy Free electrons hopping on hyperbolic lattices, constructed by periodically tilling regular p-gon with q nearest-neighbor sites on a curved space of negative curvature can harbor a variety of emergent band structures. In particular, for even p, they can be grouped into three broad categories: (a) hyperbolic Fermi liquids, (b) hyperbolic Dirac liquids and (c) hyperbolic flat bands, respectively accommodating constant, vanishing and divergent density of states near the half-filling. Irrespective of these microscopic details, from numerical self-consistent Hartree-Fock analyses we show that the nearest-neighbor (V1) and on-site (U) Coulomb repulsions respectively gives rise to charge-density-wave and antiferromagnet orders featuring staggered pattern of average electronic density and magnetization in all these systems. Both quantum orders open a mass gap near the charge neutrality point. While these orderings take place for infinitesimal strength of Coulomb interactions in hyperbolic Fermi liquid and flat bands, on hyperbolic Dirac materials such orderings take place beyond critical couplings via a quantum phase transition. We also present the scaling behavior of such mass gaps with interaction strengths, as well as showcase their spatial variations. |
Friday, March 10, 2023 1:18PM - 1:30PM |
Z55.00010: Stochastic Series Expansion Algorithm for t-J Model Doped by a Single Hole Zhan Wang In Quantum Monte Carlo (QMC) simulations, Stochastic Series Expansion (SSE) algorithm has been successfully applied to study quantum magnetism, such as the isotropic Heisenberg model. The directed loop algorithm improves the loop update strategy and can give an efficient simulation to the anisotropic XXZ model. In our work, we develop an algorithm based on the directed loop algorithm to study the t-J model doped by a single hole. Because of the hole hopping term, the model will have a sign problem if the interaction in XY direction is anti-ferromagnetic, while sign-problem-free for ferromagnetic XY interactions. Moreover, the ferromagnetic partition function corresponds to the absolute-weight sum of the case with sign-problem. It has recently been shown that such a free energy difference can be captured by the average sign in QMC simulations. |
Friday, March 10, 2023 1:30PM - 1:42PM |
Z55.00011: Quantum many-body approach to orbital magnetization Mengxing Ye Orbital magnetization originates from the orbital motion of electrons in a crystalline solids without time-reversal symmetry, and can be measured and imaged experimentally. While the theory of orbital magnetism in noninteracting systems have been developed for more than a decade, a full quantum approach applying to general correlated electron systems is still lacking. We introduce a new quantum many-body approach to compute orbital magnetization for general interacting systems, and discuss its application to time-reversal symmetry broken Fermi liquids and narrow band systems. |
Friday, March 10, 2023 1:42PM - 1:54PM |
Z55.00012: Monte Carlo Studies of the Effect of Anisotropy on Curie Temperature of 2D Heisenberg Spin Models in Honeycomb Lattices Xiuping Tao, Donovan Pettice, Mina S Perez, Holden a Hankerson Both anisotropic exchange and single-ion anisotropy can stabilize long-range magnetic order in 2D van der Waals (vdW) materials. In this study, we use Monte Carlo simulations to determine how Curie temperature (Tc) depends on the two kinds of anisotropy in 2D Heisenberg spin models in honeycomb lattices, which can represent many 2D vdW materials. Understanding Tc dependence on anisotropy helps to discover high-Tc 2D magnetic materials desired in a wide range of potential applications such as spintronic devices. |
Friday, March 10, 2023 1:54PM - 2:06PM |
Z55.00013: Database of magnetic materials in two dimensions from first principles Andres Tellez Mora, He Xu, Eric Bousquet, Ludger Wirtz, Aldo H Romero Since the experimental observation of two-dimensional (2d) ferromagnetism in a CrI3 monolayer, there has been a growing interest in finding magnetic 2d-materials with high critical temperatures, stability at ambient conditions, and new properties that could potentially improve current 2d-technologies. Nevertheless, only a few 2d-magnetic structures have been reported compared to their three-dimensional counterparts, where the highest critical temperature happens around room temperature. In this talk, we present the development of a database of 2d-magnetic materials from first-principles calculations, where we compute valuable properties such as the critical temperature, the isotropic and anisotropic exchange constants up to a long range, the Dzyaloshinskii–Moriya interaction tensor, and the magnetostatic energy. Additionally, we implement a method to deal with the problem of finding the magnetic ground state of any structure. Initially, this database contains 1526 2d-structures, 647 of which present a ferromagnetic character. Among them, 96 give a considerable exchange interaction energy and a high critical temperature. Moreover, we compare some of our results against known experimental data. |
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