Thickness dependent band structure of α-bismuthene grown on epitaxial graphene

Abstract

Along with the great interest in two-dimensional elemental materials that has emerged in recent years, atomically thin layers of bismuth have attracted attention due to physical properties on account of a strong spin–orbit coupling. Thickness dependent electronic band structure must be explored over the whole Brillouin zone in order to further explore their topological electronic properties. The anisotropic band structures along zig-zag and armchair directions of α-bismuthene (α-Bi) were resolved using the two-dimensional mapping of angle-resolved photoemission spectra. An increase in the number of layers from 1- to 2-bilayers (BLs) shifts the top of a hole band on line to high wavenumber regions. Subsequently, an electron pocket on line and a hole pocket centred at point appears in the 3 BL α-Bi. Gapless Dirac-cone features with a large anisotropy were clearly resolved on point in the 1-BL and 2-BL α-Bi, which can be attributed to the strong spin–orbit coupling and protection by the nonsymmorphic symmetry of the α-Bi lattice.