Time-reversal symmetry and circular polarized perturbation

Abstract

Topological states have commonly been cited as a new classification of materials, and global properties immune to local perturbations have been suggested as topological non-trivial attributes. Actual computations of the topological quantities of real materials have been obtained through the theories of linear responses over the static ground electronic structure. Here, we propose an alternative way by considering the time-evolution of the Hamiltonian, which lets the pumping parameter run periodically through the geometric space of the Hamiltonian. As test examples of this method, we present a trivial insulator, a spin-frozen valley-Hall system, a spin-frozen Haldane-Chern insulator, and a quantum spin-Hall insulators. In later part, we also demonstrate the spin precession dynamics of MoS2, in which the spin is strongly coupled to the optical phonon. This dynamical spin state can be resolved into discrete Floquet-phononic spectra, and once the phonon is pumped so as to break time-reversal symmetry, the resulting spin-Floquet structures induce net out-of-plane magnetizations in the otherwise non-magnetic 2D material.