We will perform a computational study of real-time charge and spin dynamics in realistic microscopic models of transition metal dichalcogenides (TMDC) on metal substrates and of TMDC/metal heterostructures. Thereby we will unveil the interplay between strain, spin-orbit coupling, and an applied time-dependent field or bias. We plan to go beyond the simple geometries where a uniform strain is applied to the TMDC, and allow for more complex systems with a non-uniform strain field, resulting in uniform or space-modulated pseudo-magnetic fields. One of our major objectives is to find a strategy to control the valley depolarization time. There are a series of control “knobs” that we can use. The obvious one is the temperature, but we can also use other external parameters such as strain (one-dimensional, two-dimensional, or non-uniform) or the interaction of the TMDC with the substrate. In fact, the coupling to the metallic substrate (magnetic or non-magnetic) may allow us to engineer the magnetization, spin-orbit coupling and electron-phonon interactions within the TMDC layer. Another important question we will address is the possibility to inject charge and spin currents from/to the TMDC.

Our main tools will be both time-dependent density functional theory (TDDFT) and time-dependent density functional tight-binding theory (TD-DFTB). The first approach will be mainly used to benchmark small systems. The TD-DFTB tool, whose development is a major part of the project, will allow us to study large systems containing thousands of atoms (a few nm in the parallel directions) over very long time-scales (on the order of ps), thereby providing access to the interplay between electron relaxation and transport, as well as to magnon and phonon dynamics.

Publications (1^st Funding Period 2018 - 2021)

• Novel two-dimensional silicon–carbon binaries by crystal structure prediction 
  P. Borlido, A. W. Huran, M. A. L. Marques, and S. Botti
  Phys. Chem. Chem. Phys. 22, 8442 (2020)  - DOI: 10.1039/C9CP06942A

• Local modified Becke-Johnson exchange-correlation potential for interfaces, surfaces, and two-dimensional materials 
  T. Rauch, M. A. L. Marques, and S. Botti 
  J. Chem. Theory Comput. 16, 2654 (2020)  - DOI: 10.1021/acs.jctc.9b01147

• Neural network force fields for simple metals and semiconductors: construction and application to the calculation of phonons and melting temperatures 
  M. R. G. Marques, J. Wolff, C. Steigemann, and M. A. L. Marques
  Phys. Chem. Chem. Phys. 21, 6506 (2019)  - DOI: 10.1039/C8CP05771K

• Structural prediction of stabilized atomically thin tin layers
  P. Borlido, A. W. Huran, M. A. L. Marques, and S. Botti
  NPJ 2D Mater. Appl. 3, 21 (2019)  - DOI: 10.1038/s41699-019-0103-9

• Propagators for the time-dependent Kohn–Sham equations: Multistep, Runge–Kutta, exponential Runge–Kutta, and commutator free Magnus methods
  A. Gómez Pueyo, M. A. L. Marques, A. Rubio, and A. Castro
  J. Chem. Theory Comput. 14, 3040 (2018)  - DOI: 10.1021/acs.jctc.8b00197

• The ground state of two-dimensional silicon
  P. Borlido, C. Rödl, M. A. L. Marques, and S. Botti
  2D Mater. 5, 035010 (2018)  - DOI: 10.1088/2053-1583/aab9ea