Tunable light-induced topological edge states in strain engineering bismuthene monolayers

Abstract

Designing quantum materials on demand is the main goal of modern condensed matter physics. In our work, we investigate the Floquet band engineering by the coherence of strain effect and periodic light fields in bismuthene, i.e., Bi (110) and Bi (111) monolayers. Bi(110) monolayer is discovered to be the elemental ferroelectric semiconductors which can host double pairs of gapless helical edge states. Our work reveals that the double pairs of gapless helical edge states is not robust to edge terminations, and circularly polarized light could drive the double pairs of gapless helical edge states into only one single pair of gapless helical edge states in Bi(110) monolayer. Moreover, for Bi(111) monolayer which hosts Z2 protected quantum spin Hall effect, light could drive the pair of helical edge states into chiral edge states. However, under different strain effect, the lightbismuthene coupled system could behave different Floquet engineering behaviors. For example, with compressive strain on Bi(111) monolayer, the light could successively drive the quantum spin Hall effect into quantum anomalous Hall effect with tunable Chern numbers. Our work demonstrates that Floquet band engineering via periodic light fields could provide a route to manipulate the edge states and topological phase transitions in bismuthene, and the coherence of strain effect and periodic light fields could play an important role in designing quantum materials on demand.