Temperature-driven modification of surface electronic structure on bismuth, a topological border material

Single crystalline bismuth is known to have a peculiar electronic structure which is very close to the topological phase transition. The modification of the surface states of Bi depending on the temperature are revealed by angle-resolved photoelectron spectroscopy. At low temperature, the upper branch of the surface state merged into the projected bulk conduction bands around the point of the surface Brillouin zone. In contrast, the same branch merged into the projected bulk valence bands at high temperature (400 K). Such behavior could be interpreted as a topological phase transition driven by the temperature, which might be applicable for future spin-thermoelectric devices. We discuss the possible mechanisms to cause such transition, such as the thermal lattice distortion and electron–phonon coupling.