Ultrafast spin dynamics on femto- to picosecond timescales is simulated within a density-operator approach for a Co/Cu bilayer. The electronic structure is represented in a tight-binding form; during the evolution of the density operator, optical excitation by a femtosecond laser pulse, coupling to a bosonic bath as well as dephasing are taken into account. Our simulations corroborate the importance of interfaces for ultrafast transport phenomena and demagnetisation processes. Moreover, we establish a reflow from Cu d orbitals across the interface into Co d orbitals, which shows up prominently in the mean occupation numbers. On top of this, this refilling manifests itself as a minority-spin current proceeding several layers into the Cu region. The present study suggests that the approach captures essential ultrafast phenomena and provides insight into microscopic processes.
@article{arxiv.2011.13763,
title = {Ultrafast spin dynamics in inhomogeneous systems: a density-matrix approach applied to Co/Cu interfaces},
author = {Franziska Töpler and Jürgen Henk and Ingrid Mertig},
journal= {arXiv preprint arXiv:2011.13763},
year = {2021}
}