Engineering Floquet topological phases using elliptically polarized light

Abstract

We study a two-dimensional topological system driven out of equilibrium by the application of elliptically polarized light. In particular, we analyze the Bernevig-Hughes-Zhang model when it is perturbed using an elliptically polarized light of frequency $\mathrm{\ensuremath{\Omega}}$ described in general by a vector potential $\mathbf{A}(t)=({A}_{0x}cos(\mathrm{\ensuremath{\Omega}}t),{A}_{0y}cos(\mathrm{\ensuremath{\Omega}}t+{\ensuremath{\phi}}_{0}))$. Even for a fixed value of ${\ensuremath{\phi}}_{0}$, we can change the topological character of the system by changing the $x$ and $y$ amplitudes of the drive. We therefore find a rich topological phase diagram as a function of ${A}_{0x}$, ${A}_{0y}$, and ${\ensuremath{\phi}}_{0}$. In each of these phases, the topological invariant given by the Chern number is consistent with the number of spin-polarized states present at the edges of a nanoribbon.