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 Q62: Quantum Many Body Systems & Methods II |
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Sponsoring Units: DCOMP Chair: Eric Switzer, Univerity of Central Florida Room: Room 417 |
Wednesday, March 8, 2023 3:00PM - 3:12PM |
Q62.00001: Efficient propagation of stochastic open quantum dynamics in coordinate space Johan F Triana, Felipe F Herrera Accurate and fast numerical solutions of the master equation in Lindblad form are important to manipulate a great variety of quantum systems for the development of quantum technologies. However, modeling strongly interacting quantized degrees of freedom is a fundamental problem due to an exponential scaling of Hilbert space. We solve the Lindblad quantum master equation by propagating quantum state trajectories in coordinate space, which involves stochastic quantum jumps. The propagation in coordinate space is performed using the multi-configuration time dependent Hartree (MCTDH) method that considerably reduces the Hilbert space or the number of equations of motion for strongly coupled oscillators. For scenarios with the number of excitations higher than one, we show the potential of our methodology in comparison with exact solutions of the density matrix in physical systems of interest in cavity quantum electrodynamics [1]. We demonstrate that it is possible to perform efficient propagations in low-RAM machines in systems whose solution with traditional methodologies requires high-RAM machines. This methodology is independent of the system under study and also works with time dependent Hamiltonians. |
Wednesday, March 8, 2023 3:12PM - 3:24PM |
Q62.00002: Defect states and defect-induced phase transition in bent transition metal dichalcogenide (TMD) nanoribbons and excitonic states SANTOSH NEUPANE, Hong Tang, Adrienn Ruzsinszky Two-dimensional (2D) transition metal dichalcogenide (TMD) materials have versatile electronic and optical properties. TMD nanoribbons show interesting properties due to reduced dimensionality, quantum confinement, and edge states. Tang et al. [1] showed that the edge bands evolved with bending can tune the optical properties for various widths of TMD nanoribbons. Defects are commonly present in 2D TMD materials, and can dramatically change the material properties. In this following work, we investigate the interaction between the edge states and the defect states in WS2 nanoribbons with line defects under different bending conditions, using the r2SCAN meta-GGA density functional [2]. We reveal interesting semiconducting-to-metallic phase transitions, suggesting potential applications in nano-electronics or molecular electronics. We also calculate the optical absorption of the nanoribbons with different defect positions with the many-body GW-BSE (Bethe-Salpeter equation) approach, revealing the tunable optical spectrum and diverse exciton states in the defected TMD nanoribbons. |
Wednesday, March 8, 2023 3:24PM - 3:36PM |
Q62.00003: A new generation of effective core potentials from correlated and spin-orbit calculations: selected transition metals and Lanthanides Haihan Zhou, Benjamin E Kincaid, Lubos Mitas, Abdulgani Annaberdiyev, Ganesh Panchapakesan, Cody A Melton We introduce new correlation consistent effective core potentials (ccECPs) for transition metals: Y, Zr, Nb, Rh, Ta, Re, Pt; Alkali metal: Cs; Lanthanides: Sm, Gd and Lu. For selected transition metals and Alkali metal, the s, p, and d orbital electrons with the highest and second highest principal quantum number are included in the valence space, while the valence space of Lanthanides additionally includes open-shell f-electrons. These ccECPs are given as a sum of spin-orbit averaged relativistic effective potential (AREP) and effective spin-orbit (SO) terms. The construction involves several steps with increasing refinements from more simple to fully correlated methods. The optimizations are carried out with objective functions that include weighted many-body atomic spectra and spin-orbit splittings. Transferability tests involve molecular binding curves of corresponding hydride and oxide dimers. The constructed ccECPs are systematically better and in a few cases on par with previous effective core potential (ECP) tables on all tested criteria and provide a significant increase in accuracy for valence-only calculations with these elements. Our study confirms the importance of the AREP part in determining the overall quality of the ECP even in the presence of sizable spin-orbit effects. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q62.00004: Dynamical tuning of the chemical potential in grand canonical Monte Carlo simulations to achieve target particle number Benjamin Cohen-Stead, Cole M Miles, Owen Bradley, Steven S Johnston, Richard T Scalettar, Kipton M Barros Here we discuss a method to adjust the chemical potential in grand canonical ensemble Monte Carlo simulations to achieve a target mean particle number that was recently introducted in Phys. Rev. E 105, 045311. The method applies a fictitious dynamics to the chemical potential that runs concurrently with the Monte Carlo sampling of the physical system. The resulting corrections to the chemical potential are made according to time-averaged estimates of the mean and variance of the particle number, with the latter being proportional to thermodynamic compressibility. We present results for a variety of tests, both within the context of classical and quantum Monte Carlo simulations, and in all cases find rapid convergence of the chemical potential---inexactness of the tuning algorithm contributes only a minor part of the total measurement error for realistic simulations. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q62.00005: Ground state and spectral properties of the doped one-dimensional optical Hubbard-Su-Schrieffer-Heeger model Debshikha Banerjee, Alberto Nocera, Jinu Thomas, Steven S Johnston Electron-phonon (e-p) coupling is believed to have an essential role in the study of many strongly correlated systems. One model that gained recent and wide interest, is the Su-Schrieffer-Heeger (SSH) model, where the atomic motion modulates the atomic hopping integrals. This model has rich and complex physics including light bipolarons and nontrivial topological properties in 1D. The introduction of the Hubbard U opens a door towards studying the interplay of strong correlations with this rich physics. For example, recent studies have found that the half-filled Hubbard SSH model supports Peierls and Mott insulating phases, but the effect of doping on this model remains unclear. Here, we study the ground and excited state properties of the doped 1D Hubbard-SSH model for a range of e-p coupling values using DMRG. In the strong coupling regime, the system tends to dimerize due to an unphysical sign change in the effective hoping, which has a strong signature in the ground state correlation. We also study the effect of phonon frequency by explicitly computing the single particle spectral function for this model. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q62.00006: On the equivalence of the bond and optical SSH models in the adiabatic limit Sohan Sanjay Malkaruge Costa, Andy Tanjaroon Ly, Benjamin Cohen-Stead, Steven S Johnston The interactions between electrons and phonons play an important role in conventional superconductivity. In general, lattice vibrations can modulate the electron potential energy, as in the Holstein model, or the electron kinetic energy ,as in the Su-Schrieffer-Heeger (SSH) model. SSH-like models have received significant attention recently as they produce qualitatively different physics in comparison to Holstein-like models. Many QMC treatments of the SSH model focus on the "bond" SSH model, which places the phonons on the atomic bonds, for various technical reasons. This is in contrast to the "optical" SSH model, where the phonons live on the individual atomic sites. Here we study the equivalence of these models in one- and two-dimensions in the adiabatic limit using semi-classical Monte Carlo. Specifically, we will present results for a systematic comparison of the models as a function of e-ph coupling, density, and dimensionality. |
Wednesday, March 8, 2023 4:12PM - 4:24PM Author not Attending |
Q62.00007: Automated algebra methods for finite-temperature quantum gasses in arbitrary dimension with the Quantum Thermodynamics Computational Engine (QTCE) Aleksander J Czejdo, Joaquín E Drut, Kaitlyn J Morrell, Nick Carter Recent progress in experimental ultracold atomic gasses provides a wide array of physical systems to test calculations from the theory side. Traditional non-perturbative methods like Monte Carlo are limited by the fermionic sign problem and the computational cost of varying lattice sizes and dimensions. The Quantum Thermodynamics Computational Engine (QTCE) provides a semi-analytic non-perturbative avenue for calculating non-interacting expectation values using a quantum cumulant expansion. In the QTCE, both fugacity and dimension enter as arbitrary numerical parameters, enabling study of dimensional crossover and computationally cheap calculations at varying temperature or chemical potential. Focusing on a non-relativistic, spin-½ Fermi system with a contact interaction, we discuss the technical aspects of the QTCE. In addition to reducing the naive high-cost calculation through traditional optimization techniques, we discuss diagram generation and graph theory methods for simplification, as well as semi-analytic integration and extrapolation, renormalization, and resummation. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q62.00008: Non-abelian symmetries in tensor networks: the open source tensor library QSpace Andreas Weichselbaum I will introduce the open-source tensor library QSpace that can deal with abelian and non-abelian symmetries in quantum tensor network simulations on a generic footing. QSpace is coded in C++ and as of now embedded into Matlab. QSpace v1 was initiated in 2006 for abelian U(1) symmetries. By 2012 QSpace v2 it had progressed to general continuous non-abelian symmetries, specifically SU(N) and Sp(2N). Major efficiency updates have been included in QSpace v3.* (2015-19) together with the implementation also of SO(N) and SO(2N+1). Based on its very history, QSpace has been extensively scrutinized and tested in the past in more than 75 research publications in a wide range of collaborations. Upon repeated request, QSpace v4 is finally going open source as a powerful versatile tool to deal with abelian and non-abelian symmetries in tensor network states. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q62.00009: Universal Features of Entanglement Entropy in the Honeycomb Hubbard Model Jonathan D'Emidio, Roman Orus Lacort, Nicolas Laflorencie, Fernando De Juan The entanglement entropy is a unique probe to access universal features of strongly interacting many-body systems. In two or more dimensions these features are subtle, and detecting them numerically requires extreme precision, a notoriously difficult task. This is especially challenging in models of interacting fermions, where many basic universal features have yet to be observed. We show how to overcome this difficulty by introducing a new formulation to measure the Rényi entanglement entropy in auxiliary-field determinental quantum Monte Carlo simulations. In this framework, the entangling region itself becomes a stochastic variable. We demonstrate the precision and efficiency of this method by extracting, for the first time, universal logarithmic terms in a two dimensional model of interacting fermions. For this purpose we study the half-filled Hubbard model at T=0, where the universal corner term is detected throughout the semi-metal phase up to the Gross-Neveu-Yukawa critical point, and Goldstone modes are observed in the Mott insulating phase. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q62.00010: Representability of Critical Phenomena in 2D Isometric Tensor Networks Karthik Siva, Sajant Anand, Zhehao Dai, Michael P Zaletel Isometric tensor networks (isoTNS) are a generalization of the canonical form of matrix product states in one dimension to tensor networks in higher dimensions. Recently it has been shown that many interesting two-dimensional quantum many-body states, such as topologically ordered states, can be represented exactly as an isoTNS, and numerical work has shown that these tensor networks can be optimized efficiently. However, the full class of quantum states which can be represented by isoTNS remains poorly understood. We make progress on this question by constructing isoTNS from cellular automata, revealing a surprisingly rich variational power of this ansatz. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q62.00011: SHORYUKEN: An Open-Source Software Package to Incorporate Nonlocal Exchange Effects for Electrons in Nanowires Yuan Chen We present an open-source software package, SHORYUKEN (Streamlined High-level Operations in Real-space to Yield, Understand, and Keep Exchange in Nanowires) for incorporating nonlocal exchange effects in nanowires with various geoemetrie, doping densities, and external boundary conditions. Calculation shows the crucial impacts of the exchange on the energy spectrum, the number of occupied states, and electron distributions of the nanosystem. In addition, we find that geometry size combined with doping density strongly influences the behaviors of electron gases. Furthermore, for the Ga-face triangular nanowires with polarizations, we consider that the origin of the electron gas is from the surface donor states and show the dependence of surface barrier height and electron density on the shell thickness. Finally, our approach is implemented with MATLAB in the SHORYUKEN open-source software package, which is made freely accessible and can be used by researchers to study the formation of electron gas. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q62.00012: Algorithm for branching and population control in correlated sampling Yiqi Yang, Siyuan Chen, Miguel A Morales, Shiwei Zhang Correlated sampling can have wide-ranging applications in quantum Monte Carlo (QMC) calculations, especially for computing energy differences or gradients in systems in proximity to each other. For example, it has been applied to chemical systems with the phaseless auxiliary field quantum Monte Carlo (AFQMC) method[1] to obtain accurate bond dissociation energies, ionization potentials, and electron affinities[2]. When branching random walks are involved, which is often the case in QMC applications, population control is typically not applied with correlated sampling, because of technical challenges. This hinders the stability and efficiency of correlated sampling, especially in larger system sizes or physically more challenging systems, when branching is more pronounced. In this work, we study schemes for allowing birth/death in correlated sampling, and propose two algorithms for population control. The first is a static method which creates a reference run and allows other correlated calculations to be added a posterior, while the second optimizes the population control for a set of correlated, concurrent runs dynamically. The two approaches are tested in different applications, including both the Hubbard model and real materials. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q62.00013: Ab initio calculations of electrical magnetochiral anisotropy with Wannier interpolation Xiaoxiong Liu, Ivo Souza, Stepan S Tsirkin Structural chirality produces characteristic responses that change signs with handedness. An example is electrical magnetochiral anisotropy (eMChA), a linear change in the resistivity of the chiral conductor in a magnetic field. A strong eMChA was recently reported in p-doped tellurium [1,2]. Motivated by these works, we have developed an ab initio methodology for evaluating the eMChA response of chiral crystals. We use the semiclassical Berry-Boltzmann formalism within the constant relaxation-time approximation to express the Ohmic current at order $E^2B$ in terms of the band energies, Berry curvature, and intrinsic orbital moment of the Bloch states, which we then evaluate numerically using Wannier interpolation. We report preliminary results for tellurium as a function of temperature and doping concentration and compare with the experiment. With an effective model, we find the velocity on the Fermi surface governs the behavior of the eMChA conductivity. |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q62.00014: High spin coherency in one-dimensional van der Waals material Yinong Zhou, Dmitri Leo M Cordova, Maxx Q Arguilla, Ruqian Wu One-dimensional van der Waals material, such as InSeI, can be exfoliated to a single wire due to the weak van der Waals interaction between the wires. We experimentally synthesize one-dimensional van der Waals materials with helical structures. Using first-principles calculations and effective Hamiltonian, we report the fixed spin orientation perpendicular to the spin current direction in this material with screw symmetry. The combination of the Rashba and Dresselhaus spin-orbit coupling effect induces the spin splitting of bands with spin-momentum locking and high spin coherency. Our results provide a promising platform for spintronic applications. |
Wednesday, March 8, 2023 5:48PM - 6:00PM |
Q62.00015: Ferroelectric Spin-Valley Coupling in van der Waals Bilayers Denzel Ayala, Tong Zhou, Cheng Gong, Igor Zutic Sliding ferroelectricity, where the out-of-plane electric polarization is switched by in-plane interlayer sliding, has been recently proposed and confirmed in numerous stacked two-dimensional van der Waals (vdW) bilayers [1-4]. This unusual ferroelectricity has sparked a great deal of interest, as it not only paves the new way for the realization of vdW ferroelectric devices, but also introduces exciting new elements to spintronics and valleytronics via ferroelectric spin-valley coupling [1]. Here, by using a low-energy effective model and first-principles calculations, we demonstrate how the sliding ferroelectricity induces spin-valley polarizations and anomalous Hall effects in vdW bilayers. Through the analysis of topology, we also illustrate the mechanism and realization of magnetic topological states using strain. Our research offers a fresh perspective to understand and manipulate the interaction between electron charge, spin, and valley degrees of freedom. |
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