Transport properties of Hall-type quantum states in disordered bismuthene

Abstract

Bismuthene, an inherently hexagonal structure characterized by a huge bulk gap, offers a versatile platform for investigating the electronic transport of various topological quantum states. Using nonequilibrium Green’s function method and Landauer-Büttiker formula, we thoroughly investigate the transport properties of various Hall-type quantum states, including quantum spin Hall (QSH) edge states, quantum valley Hall kink (QVHK) states, and quantum spin-valley Hall kink (QSVHK) states, in the presence of various disorders. Based on the exotic transport features, a spin-valley filter, capable of generating a highly spinand valley-polarized current, is proposed. The valley index and the spin index of the filtered QSVHK state are determined by the staggered potential and the intrinsic spin-orbit coupling, respectively. The efficiency of the spin-valley filter is supported by the spacial current distribution, the valley-resolved conductance, and the spin-resolved conductance. Compared with a sandwich structure for QSVHK, our proposed spin-valley filter can work with a much smaller size and is more accessible in the experiment.