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

## TL;DR

This study investigates how temperature influences the surface electronic structure of bismuth, revealing a potential temperature-driven topological phase transition with implications for spin-thermoelectric applications.

## Contribution

It provides experimental evidence of temperature-dependent surface state modifications in bismuth, suggesting a possible topological phase transition driven by thermal effects.

## Key findings

- Surface states merge with bulk conduction bands at low temperature.
- Surface states merge with bulk valence bands at high temperature (400 K).
- Temperature influences the topological nature of bismuth's surface electronic structure.

## Abstract

Single crystalline bismuth (Bi) 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 (ARPES). At low temperature, the upper branch of the surface state merged to the projected bulk conduction bands around the $\bar{M}$ point of the surface Brillouin zone (SBZ). In contrast, the same branch merged to 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.