Bulk-edge correspondence and new topological phases in periodically driven spin-orbit coupled materials in the low frequency limit

TL;DR

This paper explores how circularly polarized light induces new topological phases in spin-orbit coupled materials like silicene and germanene, especially in the low-frequency regime, revealing complex spin-resolved edge states and phase transitions.

Contribution

It uncovers new topological phases in periodically driven spin-orbit materials beyond the high-frequency limit, characterized by novel spin-resolved invariants and gap closure mechanisms.

Findings

Identification of new topological phases with spin-resolved invariants

Gap closures occur at high symmetry points in the Brillouin zone

Discovery of phase transitions induced by low-frequency light

Abstract

We study the topological phase transitions induced in spin-orbit coupled materials with buckling like silicene, germanene, stanene, etc, by circularly polarised light, beyond the high frequency regime, and unearth many new topological phases. These phases are characterised by the spin-resolved topological invariants, $C_0^\uparrow$, $C_0^\downarrow$, $C_\pi^\uparrow$ and $C_\pi^\downarrow$, which specify the spin-resolved edge states traversing the gaps at zero quasi-energy and the Floquet zone boundaries respectively. We show that for each phase boundary, and independently for each spin sector, the gap closure in the Brillouin zone occurs at a high symmetry point.