Title: Predictive Theory for Non-Equilibrium Quantum Many-Body Systems
Abstract:
Reliable prediction of materials’ quantum properties driven out of equilibrium is critical in various fields from semiconductor spintronics, energy conversion, continuous and discrete quantum information science and technology.
Here we will introduce our recently developed real-time first-principles density-matrix dynamics (FPDMD) method for open quantum systems in solids. We derive this theory based on the time evolution of the electronic density matrices capable of treating electron-environment interactions and electron-electron correlations at the same level of description. The effect of the environment is separated into a coherent contribution, like the coupling to applied external electro-magnetic fields, and an incoherent contribution, like the interaction with lattice vibrations or the thermal background of radiation. Electron-electron interaction is formally derived using the nonequilibrium Green’s function plus generalized Kadanoff-Baym ansatz. The obtained non-Markovian coupled set of equations reduces to ordinary Lindblad quantum master equation form in the Markovian limit.
We show this first-principles framework enables us to make reliable prediction of quantum observables and quasiparticle dynamics in- and out- of equilibrium from strong to weak coupling limit. We further extend this framework with Wigner functions for simulating spatial-temporal quantum dynamics and transport accounting for a range of quantum degrees of freedom. As examples, we show our accurate predictions of relaxation and decoherence time of spin and orbital angular momentum of electron carriers in solids, dynamics of excitons and magnons, nonlinear photocurrents generated from electron-phonon scatterings, as well as spatial-temporal quantum transport simulations that explain how chiral materials being a dynamical spin polarizer that generates spin without external magnetic field or intrinsic magnetization.
Bio:
Yuan Ping received her B.Sc. degree from University of Science and Technology of China in 2007, Ph.D. from UC Davis in 2013, and materials postdoctoral fellow at Caltech in 2016. From then she was an assistant and associate professor in chemistry and affiliated professor in physics at UC Santa Cruz. From July 2023, she moved to UWMadison as associate professor in Materials Science and Engineering, and affiliated professor in physics and chemistry. Her research group focuses on developing first-principles many-body theory and quantum dynamics for materials applications. Ping is a recipient of Alfred P. Sloan Research Fellow, NSF CAREER Award, Air Force YIP award, and ACS COMP OpenEye Award. Ping is the lead of DOE Computational Chemical Science center (ADEPTs), the thrust lead of spin phenomena of DOE Computational Materials Science Center (NENPQ), as well as the thrust lead of the Energy Frontier Research Center (CHOISE).