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 [1]. 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 polaronic interactions, and an incoherent contribution, like the interaction with lattice vibrations, which leads to relaxation and decoherence. 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 [1,2].

We show this first-principles framework enables us to make reliable prediction of quantum observables and quasiparticle dynamics in- and out- of equilibrium for both coherent and incoherent processes. As examples, we show our accurate predictions of relaxation and decoherence time of spin of electron carriers in solids [3-5], dynamics of excitons [6] and magnons, nonlinear photocurrents (photogalvanic effects) generated from electron-phonon scatterings.

At 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 spin diffusion length prediction of graphene/hBN at room temperature including electron-phonon couplings [7]. And 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 [8].

References:

[1] “First-principles open quantum dynamics for solids based on density-matrix formalism”, J. Simoni, G. Riva, and Y. Ping, J. Chem. Phys, 163, 170901 (2025)

[2] “Ab initio ultrafast spin dynamics in solids”, J. Xu, A. Habib, F. Wu, R. Sundararaman and Y. Ping, Phys. Rev. B, 104,184418 (2021)

[3] “Spin-phonon 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)

[4] “Ab-initio Predictions of Spin Relaxation, Dephasing and Diffusion in Solids”, J. Xu and Y. Ping, J. Chem.Theory Comput., 20, 492, (2023)

[5] “How Spin Relaxes and Dephases in Bulk Halide Perovskites”, J. Xu, K. Li, U. Huynh, J. Huang, R.Sundararaman, V. Vardeny, and Y. Ping, Nat. Commun., 15, 188, (2024)

[6] “Phonon-Assisted Radiative Lifetimes and Exciton Dynamics from First Principles”, C. Guo, G. Riva, J. Xu, J. Simoni, Y. Ping, Phys. Rev. B (Letters), 112, L161111 , (2025).

[7] “Spatio-temporal spin transport from first principles“, M. Fadel, J. Quinton, M. Chandra, M. Gupta, Y. Ping∗, and R. Sundararaman*, submitted, (2025) https://www.arxiv.org/pdf/2505.07745

[8] “The role of orbital polarization and spin-dependent electron-phonon scatterings in chiral-induced spin selectivity“, M. Gupta, A. Grieder, M. Fadel, J. Simoni, J. Yu, R. Sundararaman, and Y. Ping, submitted, (2025), https://arxiv.org/abs/2508.03886