Light-induced above-room-temperature Chern insulators in group-IV Xenes

Floquet engineering provides a versatile platform for realizing and manipulating diverse exotic topological phases inaccessible in equilibrium. Under the irradiation of circularly or elliptically polarized light, the sizable spin-orbit couplings in group-IV Xene materials (e.g., silicene, germanene, stanene) lead to topological phase transitions (TPT) from quantum spin Hall (QSH) to quantum anomalous Hall (QAH) states, governed by spin-degeneracy broken with band closing and reopening process in one of the spin components. Fascinatingly, a large gapped (≥35 meV) QAH effect with a Chern number C = ± 2 can be introduced under a wide range of laser parameters, lifting limitations of conventional atomic building blocks to achieve long-range magnetism and enabling Chern-insulating behaviors above room temperature. A complex phase diagram for such TPTs is predicted. This work addresses transitions between two-dimensional QSH and QAH states via Floquet engineering, which will stimulate experimental realization of above-room-temperature QAH in group-IV Xenes.