Doubled quantum spin Hall effect with high-spin Chern number in ?-antimonene and ?-bismuthene

The discovery of the quantum spin Hall effect (QSHE) has ignited the field of topological physics with a vast variety of exotic properties. Here we present the emergence of doubled QSHE in two dimensions characterized with a high-spin Chern number of CS = 2 and two pairs of helical edge states. Although overlooked and invisible in topological quantum chemistry and symmetry indicator theory, the already experimentally synthesized ??-antimonene and ??-bismuthene (??-Bi) are revealed as realistic material candidates of predicted topological states with band inversions emerging at generic k points, rather than the high-symmetry momenta. Remarkably, the nontrivial energy gap can be as large as 342 meV for ??-Bi, indicating the high possibility of room-temperature observation of the doubled QSHE. Moreover, a four-band effective model is constructed to demonstrate further the feasibility of attaining this type of nontrivial topology. Our results not only uncover a novel topological character of antimony and bismuth but also facilitate the experimental characterization of the previously overlooked hidden topology.

Automated summary

This study presents the emergence of doubled QSHE in two dimensions characterized by a high-spin Chern number of CS = 2, utilizing β-antimonene and β-bismuthene as potential material candidates with band inversions at generic k points.