Condensed Matter/Materials & Biological Physics Seminar

Spin and Exciton Dynamics in Quantum Materials from First-principles

Yuan Ping (Hosted by Yang), University of California - Santa Cruz

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. 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 [1].

Recently, we implemented real-time DM dynamics for ultrafast Kerr rotation and studied spin dynamics under external electrical and magnetic field.  We found the peculiar spin 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 (R), 2, 124002, (2018).
  6. T. Smart, K. Li, J. Xu, Y. Ping, under review, arxiv.2009.02830