BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:First-principles open quantum dynamics based on a density-matrix f ormalism for spin-optotronic properties in solids  - Yuan PING (Universi ty of Wisconsin - Madison) DTSTART:20251212T151500Z DTEND:20251212T163000Z UID:TALK235582@talks.cam.ac.uk CONTACT:Bo Peng DESCRIPTION:Reliable prediction of materials' quantum properties driven ou t of equilibrium is critical in various fields from semiconductor spintron ics\, energy conversion\, continuous and discrete quantum information scie nce and technology.\n \nHere we will introduce our recently developed real -time first-principles density-matrix dynamics (FPDMD) method for open qua ntum systems in solids [1]. We derive this theory based on the time evolu tion of the electronic density matrices capable of treating electron-envir onment interactions and electron-electron correlations at the same level o f description. The effect of the environment is separated into a coherent contribution\, like the coupling to applied external electro-magnetic fie lds and polaronic interactions\, and an incoherent contribution\, like the interaction with lattice vibrations\, which leads to relaxation and decoh erence. Electron-electron interaction is formally derived using the noneq uilibrium Green's function plus generalized Kadanoff-Baym ansatz. The obta ined non-Markovian coupled set of equations reduces to ordinary Lindblad q uantum master equation form in the Markovian limit [1\,2].\n \nWe show thi s first-principles framework enables us to make reliable prediction of qua ntum observables and quasiparticle dynamics in- and out- of equilibrium fo r both coherent and incoherent processes. As examples\, we show our accura te predictions of relaxation and decoherence time of spin of electron carr iers in solids [3-5]\, dynamics of excitons [6] and magnons\, nonlinear p hotocurrents (photogalvanic effects) generated from electron-phonon scatte rings.\n \nAt the end we show 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. We show accurate spi n diffusion length prediction of graphene/hBN at room temperature includin g electron-phonon couplings [7]. And spatial-temporal quantum transport si mulations that explain how chiral materials being a dynamical spin polariz er that generates spin without external magnetic field or intrinsic magnet ization [8].\n \nReferences:\n\n[1] “First-principles open quantum dynam ics for solids based on density-matrix formalism”\, J. Simoni\, G. Riva\ , and Y. Ping\, J. Chem. Phys\, 163\, 170901 (2025)\n\n[2] “Ab initio ul trafast spin dynamics in solids”\, J. Xu\, A. Habib\, F. Wu\, R. Sundara raman and Y. Ping\, Phys. Rev. B\, 104\,184418 (2021)\n\n[3] “Spin-phono n relaxation from a universal ab initio density-matrix approach”\, J. Xu \, A. Habib\, S. Kumar\, F.Wu\, R. Sundararaman\, and Y. Ping Nat. Commun. \, 11\, 2780\, (2020)\n\n[4] “Ab-initio Predictions of Spin Relaxation\, Dephasing and Diffusion in Solids”\, J. Xu and Y. Ping\, J. Chem.Theory Comput.\, 20\, 492\, (2023)\n\n[5] “How Spin Relaxes and Dephases in Bu lk Halide Perovskites”\, J. Xu\, K. Li\, U. Huynh\, J. Huang\, R.Sundara raman\, V. Vardeny\, and Y. Ping\, Nat. Commun.\, 15\, 188\, (2024)\n\n[6] “Phonon-Assisted Radiative Lifetimes and Exciton Dynamics from First Pr inciples”\, C. Guo\, G. Riva\, J. Xu\, J. Simoni\, Y. Ping\, Phys. Rev. B (Letters)\, 112\, L161111\, (2025).\n\n[7] “Spatio-temporal spin trans port from first principles“\, M. Fadel\, J. Quinton\, M. Chandra\, M. G upta\, Y. Ping∗\, and R. Sundararaman*\, submitted\, (2025) https://www .arxiv.org/pdf/2505.07745\n\n[8] “The role of orbital polarization and s pin-dependent electron-phonon scatterings in chiral-induced spin selectivi ty“\, M. Gupta\, A. Grieder\, M. Fadel\, J. Simoni\, J. Yu\, R. Sundarar aman\, and Y. Ping\, submitted\, (2025)\, https://arxiv.org/abs/2508.03886 LOCATION:Seminar Room 3\, RDC. END:VEVENT END:VCALENDAR