Theoretical study on large gap quantum spin Hall materials – Bismuthene

Quantum spin Hall (QSH) and quantum anomalous Hall (QAH) effects hold great promise for future applications in spintronics and quantum computations. So far, their emergence has been limited to ultralow temperatures. A large topological gap is critical to increasing the operating temperature. We demonstrate that a px-py model on the honeycomb lattice with local spin-orbital coupling (SOC) favors a large topological gap. A prototype material to realize such a scenario is the two-dimensional honeycomb layer formed by bismuth atoms, i.e. bismuthene. The theoretical paradigm of such a high-temperature QSH effect can nicely extend to other group-V elements, different substrates, and even correlated d-orbital systems. As examples, we further show bismuthene/SiO₂ and iron-halogenide as large-gap QSH and QAH insulators described by px-py and d_xy-d_x2-y2 models, respectively.