Designing new quantum materials with long-lived electron spin states is in urgent need of a general theoretical formalism and computational technique to reliably predict spin lifetimes. We present a new, universal first-principles methodology based on density matrix (DM) dynamics for open quantum systems to calculate the spin-phonon relaxation time of solids with arbitrary spin mixing and crystal symmetry. In particular, this method describes contributions of the Elliott-Yafet (EY) and D’yakonov-Perel’ (DP) mechanisms to spin relaxation, corresponding to systems with and without inversion symmetry, on an equal footing[1]. Our ab initio predictions are in excellent agreement with experimental data for a broad range of materials, such as Si, Fe, MoS₂, graphene and its interfaces as well as GaAs.   Recently, we implemented real-time DM dynamics for ultrafast Kerr rotation and studied spin dynamics under external electric and magnetic field.  We found a peculiar spin lifetime anisotropy under external electric field for graphene/hBN interface beyond the traditional DP picture, but consistent with experiments. Work in progress is to include e-e and e-impurity scattering to study spin dynamics at low temperature and other topological two-dimensional materials and their interfaces.  

In addition, we will also introduce our recent work on radiative and nonradiative exciton recombination in two-dimensional systems from many-body perturbation theory and its applications on designing point defects as single photon emitter and spin qubits in hexagonal BN[2-6].  Our work underscores the predictive power of first-principles techniques for key physical properties to quantum information science.

References:  

[1]  J. Xu, A. Habib, S. Kumar, F. Wu, R. Sundararaman, and Y. Ping, Nature Communications, 11, 2780, (2020) 

[2]  F. Wu, T. Smart, J. Xu, Y. Ping, Physical Review B, 100, 081407(R) (2019)

[3]  F. Wu, D. Rocca and Y. Ping, Journal of Materials Chemistry C, 7, 12891, (2019)

[4]  F. Wu, A. Galatas, R. Sundararaman, D. Rocca, and Y. Ping, Physical Review Materials, 1, 071001(R), (2017). 

[5]  T. Smart, F. Wu, M. Govoni and Y. Ping, Physical Review Materials, 2, 124002, (2018).

[6]  T. Smart, K. Li, J. Xu, Y. Ping, under review, arXiv:2009.02830, (2020)

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