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 F59: First-Principles Simulations of Excited-State Phenomena: GW Method and Beyond II |
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Sponsoring Units: DCOMP Chair: Sohrab Ismail-Beigi, Yale University Room: Room 301 |
Tuesday, March 7, 2023 8:00AM - 8:12AM |
F59.00001: Quasiparticle Self consistent GW with ladder diagrams in W Mark van Schilfgaarde, Brian Cunningham, Myrta Grüning, Dimitar Pashov We present an extension of the quasiparticle self-consistent GW approximation (QSGW) to include vertex corrections in the screened Coulomb interaction W. This is achieved by solving the Bethe-Salpeter equation for the polarization matrix at all k-points in the Brillouin zone. QSGW yields a good and consistent description of the electronic structure and optical response, but systematic errors in several properties appear, A primary object of this paper is to assess to what extent including ladder diagrams in W ameliorates systematic errors in the QSGW approximation: notably a tendency to overestimate insulating bandgaps, blue-shift plasmon peaks in the imaginary part of the dielectric function, and underestimate the dielectric constant. We find ladders do ameliorate shortcomings of QSGW in insulators to a remarkable degree, and provide a high fidelity description both the one-body Green's function and the dielectric function, for a wide range of insulators. Some discrepancies remain, we show to what extent the errors are systematic and can be traced to diagrams missing from the theory. Another finding of this work is to establish the distinction between the optical gap and fundamental gap in some commonly studied materials, such as SrTiO3 and CuAlO2. |
Tuesday, March 7, 2023 8:12AM - 8:24AM |
F59.00002: Dynamical renormalization of interactions in downfolded Hamiltonians with the stochastic cRPA Mariya Romanova, Vojtech Vlcek, Guorong Weng, Arsineh Apelian The model downfolded Hamiltonians facilitate the electronic structure calculations by reducing the computational load, however, several methodological issues can compromise the accuracy of this approach. Among them is an accurate inclusion of the environment dynamics that translates into the frequency dependence of one- and two-body interaction terms, which is often overlooked. |
Tuesday, March 7, 2023 8:24AM - 8:36AM |
F59.00003: On the relation between the GW approximation and (Unitary) Coupled Cluster theory Johannes F Tölle, Garnet K Chan The first formal connection between the particle-hole (ph) random phase approximation (RPA) and the so-called ring-Coupled Cluster (CC) formalism has been established by Scuseria et al. in 2008.1 |
Tuesday, March 7, 2023 8:36AM - 8:48AM |
F59.00004: All-electron BSE@GW method for Extended Systems with Numeric Atom-Centered Orbitals Ruiyi Zhou, Yi Yao, Volker Blum, Yosuke Kanai BSE@GW method has emerged as a powerful many-body perturbation theory approach not only in condensed matter physics but also in quantum chemistry in recent years. Over the last several years, we have been developing a new all-electron implementation of the BSE@GW formalism using numeric atom-centered orbital basis sets in FHI-aims code. In this talk, we will discuss our recent developments in implementing this formalism for extended systems with the periodic boundary conditions. We will discuss its implementation and numerical challenges. We will present various convergence tests pertaining to numerical atomic orbitals, auxiliary basis set for the resolution-of-identity formalism, and Brillion zone sampling, etc. Several proof-of-principle examples will be presented to compare with other formalisms, illustrating the new all-electron BSE@GW method for extended systems. |
Tuesday, March 7, 2023 8:48AM - 9:00AM |
F59.00005: Cubic-Scaling Canonical GW Formulation for Solids based on Tensor Hyper-Contraction Chia-Nan Yeh, Miguel A Morales We present a cubic-scaling canonical GW formulation for solids based on tensor hyper-contraction (THC). The THC factorization results in a separable form of electron repulsion integrals (ERIs) in a generic discretized single-particle basis, and therefore allows a reformulation of the canonical GW (THC-GW) that shares the same complexity as in the space-time formalism. The THC-GW formalism scales linearly with respect to the number of k-points, and cubicly with respect to the size of the unit cell. Due to the compactness of discretized single-particle bases compared to the real-space grid, THC-GW has a much smaller prefactor in its complexity than the space-time formalism. The low scaling of THC-GW does not rely on a single-particle picture or sparsity of matrix elements. Therefore, it is directly applicable to different variants of GW, including the fully self-consistent GW, and the accuracy is solely controlled by the error of the THC factorization. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F59.00006: Development of GW-based substrate screening methods for strongly coupled molecule-metal interfaces Joseph Frimpong, Zhenfei Liu The understanding of the molecule-metal interfaces is of paramount importance to the development of novel electronic devices. This requires an accurate characterization of the quasiparticle electronic structure at these heterogeneous interfaces, for which the GW approach within the framework of many-body perturbation theory is generally accurate. The substrate screening approximation effectively reduces the computational cost of GW calculations for large weakly coupled interfaces, by assuming that the non-interacting polarizability of the interface is additive of those from the adsorbate and from the substrate. However, this approximation breaks down for strongly coupled interfaces. Here, we develop a new GW-based method that captures the significant orbital hybridization at the interface, extending the substrate screening approximation. We use two experimentally well-studied systems to demonstrate our approach, namely the benzene dithiol adsorbed on Au(111) and the naphthalene tetracarboxylic dianhydride adsorbed on Ag(111). Our work holds promise in studying a wide range of interfaces including defects, covalently bound molecules on metal surfaces, and many others. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F59.00007: Stochastic Real-Time Second-Order Green's Function Theory for Neutral Excitations in Molecules and Nanostructures Leopoldo Mejia, Jia Yin, David Reichman, Roi Baer, Chao Yang, Eran Rabani We present a real-time second-order Green's function method (TD-GF2) for computing neutral excitations in molecules and nanostructures. The framework is combined with the stochastic resolution of the identity to decouple the 4-index electron repulsion integrals (ERI) in the system Hamiltonian. This leads to the reduction of the computational cost to $O(N^3)$ with system size. The stochastic implementation recovers deterministic results for the electronic dynamics and excitation energies, and reproduces benchmark results from the analogous linear-response implementation in frequency. This approach is further combined with the Dynamic Mode Decomposition (DMD) technique to predict the nonlinear long-time dynamics of the density matrix. The statistical error due to the incorporation of the stochastic resolution of the identity and DMD extrapolation is analyzed in terms of the number of stochastic orbitals, system size, and propagation time. Overall, this approach offers an efficient route to investigate excited states in finite systems containing hundreds of electrons. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F59.00008: Embedding Vertex Correction in Stochastic GW Self-Energy Guorong Weng, Vojtech Vlcek I will present a stochastic vertex-corrected $GWGamma$ method that embeds vertex correction in the one-shot GW (G0W0) self-energy. The embedding scheme starts with partitioning the single-particle space into an active space and the its orthogonal complement (denoted the environment). The active space is defined by energetically-active states that can be eigenstates of a mean-field Hamiltonian, chemical bonds of molecular systems, or Wannier functions of an energy band. I will introduce our latest algorithmic development in Pipek-Mezey localization, which renders a linear scaling approach for obtaining regionally localized states on a subsystem. The core step of our embedding scheme is to perform the "separation-propagation-recombination" treatment on the random vectors that sample the Green's function and the induced density and density matrix fluctuations. The active component of a random vector is treated specially with vertex, while the environment is not. The proposed embedding method is applied to various chemical systems, including donor-acceptor (D-A) complexes, D-A copolymer, and D-A double layers with up to 2000 electrons. Single-particle states featuring low-energy charge-transfer excitation are chosen to form the active space. Computational results with embedded vertex correction significantly improve the fundamental gap prediction upon the G0W0 approximation. Active spaces with varied sizes and basis sets are tested. The size effect is critical to the prediction of electron affinity. The change of basis for the active space can simplify the screening calculation. Furthermore, I will demonstrate the separation of the vertex correction into two terms: the correction to the polarizability and the Gamma term. The first term is found to destabilize the quasiparticle energies consistently, while the second term contributes differently to occupied and unoccupied states. |
Tuesday, March 7, 2023 9:36AM - 9:48AM Author not Attending |
F59.00009: Quasiparticle, exciton, and optical properties in violet and blue phosphorenes Ju Zhou, Tian-Yi Cai, Sheng Ju Strong many-body effects arising from enhanced electron-electron and electron-hole interactions will give rise to novel phenomena in two-dimensional (2D) materials. Accurate computational method like ab initio many-body perturbation theory is necessary to calculate the quasiparticle and optical properties in 2D materials [1]. In this talk, we will discuss our G0W0-BSE calculations on violet (Hittorf's) and blue phosphorenes, two new 2D candidates in the phosphorus allotropes family. We first demonstrate a direct-wide-band-gap semiconductor with anisotropic electron-hole excitation of Hittorf's phosphorene monolayer [2]. In addition, the relatively large thickness makes it possible to modulate the band gap and optical properties substantially via a vertical electric field and this strong quantum-confined Stark effect shows its potential in 2D optoelectronics devices [3]. For blue phosphorene, we reveal the unusual strain dependence of quasiparticle, optical, and exciton properties, where the funnel effect could be realized to overcome its indirect-band-gap nature for the green or blue light-emitting applications [4]. We also show the stronger exciton effect in few-layer blue phosphorene [5]. Compared to other 2D materials [6], it was revealed that the parallel band structure in these indirect band gap semiconductors plays a crucial role. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F59.00010: First principles calculation of valley g-factors in transition metal dichalcogenide monolayers, with dynamical self-energy effects. Fengyuan Xuan, Su Ying Quek H-phase transition metal dichalcogenide (TMD) monolayers (MLs) have two distinct energy valleys, and are therefore promising for valleytronic applications, in which the valley degree of freedom is controlled for information storage and processing. In the presence of an out-of-plane magnetic field, the two valleys are shifted in opposite directions (the Zeeman effect), and reorganised into discrete equally-spaced levels (Landau Levels). The Zeeman effect is quantified by the Landé g-factor. Here, we develop an approach which provides quantitative predictions of the g-factors, taking into account many-body interactions from first principles.[Phys. Rev. Res. 2, 033256; npj Comput. Mater. 7, 198] We show that dynamical self-energy effects can significantly enhance the g-factors of doped ML TMDs, compared to undoped TMDs.[npj Comput. Mater. 7, 198] The predicted g-factors are in excellent agreement with experimentally-determined doping-density-dependent enhanced valley g-factors, g*.[Phys. Rev. Lett. 125, 147602] This enhancement effect is shown to orginate from the varying screened exchange interaction in response to the change of doping density in the two valleys. We predict the presence of a critical magnetic field after which this enhencement effect will disappear. Our calculated critical magnetic fields agree with recent experimental measurements.[Phys. Rev. Lett. 125, 147602] |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F59.00011: Molecular Insights into Optical Spectroscopy of Liquid Water and Ice Fujie Tang, Zhenglu Li, Chunyi Zhang, Diana Y Qiu, Xifan Wu Optical spectroscopy is a powerful experimental technique to probe the electronic structure of water. An accurate modeling of optical spectra demands accurate descriptions of both molecular structures and electron-hole excitation processes from first principles. Using the equilibrated molecular structure obtained by the state-of-the-art deep potential path-integral molecular dynamics simulations with the density-functional theory data at the levels of SCAN0 hybrid functional, we compute optical spectra of liquid water and ice by solving the GW-Bethe-Salpeter equation as implemented in the BerkeleyGW package. Our theoretical optical spectrum agrees well with existing experiments. We further assign the peaks with molecular orbitals and identify the molecular motifs for the optical excitons in ice and liquid water. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F59.00012: Quantitative many-body electronic structure of CaCuO2 and LaNiO2 from all-orbital DMFT Linqing Peng, Huanchen Zhai, Tianyu Zhu, Garnet K Chan Dynamic mean-field theory (DMFT) with a downfolded correlated space has been widely used to study the many-body electronic structure of high Tc cuprate superconductors and their analog nickelates. Yet, different downfolding of correlated space from various localization schemes has yielded significantly different quasiparticle mass renormalization for both parent compounds and has even led to qualitatively different predictions in NdNiO2 over the importance of Hund’s and charge transfer physics [1]. To quantitatively capture the electron correlations, we applied a recently developed all-orbital GW+DMFT theory to CaCuO2 and LaNiO2 in the paramagnetic phase where all valence and virtual orbitals within a unit cell are included in the correlated space without downfolding. With an active-space DMRG solver suited to capture strong correlations, the calculated quasiparticle mass renormalization agrees to an order of magnitude better accuracy across correlated space from three different localizations compared to the downfolded DMFT results. Furthermore, we provide insights on downfolding by analyzing the importance of degrees of freedom near the Fermi level. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F59.00013: Charge asymmetry in HD+ ion and HD molecule Saeed Nasiri, Sergiy Bubin, ludwik Adamowicz Within the framework of the variational method without assuming the Born-Oppenheimer (BO) approximation we consider vibrational states of the HD+ and HD molecular species in the ground rotational state. The three- and four-particle non-BO wave functions of these systems are expanded in terms of two types of all-particle explicitly correlated Gaussian (ECG) basis functions – the complex ones and real ones with prefactors in the form of powers of the internuclear distance. The non-BO variational wave functions are used to calculate the proton, deuteron, and electron probability densities and pair correlation functions, which are then compared with the corresponding probability densities obtained from pure BO calculations and from BO calculations that include the diagonal BO corrections. The charge asymmetry in the two systems that originates from the isotopic H/D mass difference are analyzed and it is found that, for the HD molecule, the asymmetry is the most significant for the v = 7-9 states, where v is the vibrational quantum number. Note that in the non-BO calculation, v is not, strictly speaking, a good quantum number, as in such a calculation the vibrational motion couples with the electronic motion. In the case of HD+ molecular ion, the particle distributions obtained from the BO calculations agree well with their non-BO counterparts up to the v = 20 state where only a tiny amount of charge asymmetry can be observed. However, for the v = 21 and v = 22 states, a complete breakdown of the Born–Oppenheimer approximation is observed. In these two states, the electron almost entirely localizes at the deuteron. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F59.00014: Scaling of Particle Entanglement Entropy in Tomonaga–Luttinger Liquids Harini Radhakrishnan, Matthias Thamm, Hatem N Barghathi, Bernd Rosenow, Adrian G Del Maestro Entanglement entropy under a particle bipartition provides complementary information to spatial bipartite entanglement as it is sensitive to interactions, particle statistics, and phase transitions to leading order. In a quantum system of $N$ particles, it quantifies the entanglement between a subset of $n$ particles and the rest of the system, and information about such entanglement is encoded in the spectrum of the corresponding $n$-particle reduced density matrix. We investigate the particle entanglement entropy in a system of $N$ spinless fermions in the Tomonaga–Luttinger liquid regime. Previous work has proposed an empirical scaling relation for the particle entanglement at fixed $n$, where the leading order term is given by the logarithm of the number of fermions $N$ plus a non-universal constant. We examine the entanglement entropy dependence on the partition size $n$ through exact diagonalization and density matrix renormalization group techniques to unprecedented system sizes. Our results support the proposed scaling and strongly suggest that interactions induce a change in the particle entanglement entropy that, to leading order in $N$, scales as $An$, where $A$ is an interaction dependent constant. Thus, the identified scaling form can be exploited to predict the $n$-particle entanglement entropy for larger systems using only the single particle reduced density matrix. |
Tuesday, March 7, 2023 10:48AM - 11:00AM |
F59.00015: All quantum spectra in one shot Carlos L Benavides-Riveros, Lipeng Chen, Sebastián Mantilla, Christian Schilling, Stefano Pittalis Determining the properties of the excitations in quantum many-body systems is a fundamental problem across almost all sciences. For instance, quantum excited states underpin new states of matter, support biological processes such as vision, or determine optoelectronic properties of photovoltaic devices. Yet, while ground-state properties can be determined by rather accurate computational methods, there remains a need for theoretical and computational developments to target excited states efficiently. Inspired by the duplication of the Hilbert space used to study black-hole entanglement and the electronic pairing of conventional superconductivity, we have recently developed a new variational scheme to compute the full spectrum of a quantum many-body Hamiltonian, rather than only its ground or the lowest-excited states. An important feature of our proposed scheme is that these spectra can be computed in a one-shot calculation. The scheme thus provides a novel variational platform for excited-state physics. Since our approach is suitable for efficient implementation on quantum computers, we believe this "variational quantum diagonalizer" has the potential to enable unprecedented calculations of excited-state processes of quantum many-body systems. To test the accuracy of the method, in this talk I will show an explicit calculation for a Fermi-Hubbard Hamiltonian, based on a unitary coupled-cluster ansatz. |
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