Spontaneous electric potential generation on the surface of the topological Kondo insulator SmB₆

In recent years, Samarium Hexaboride (SmB₆) has received renewed attention due to its identification as a three-dimensional topological Kondo insulator (3D TKI). Understanding the precise mechanisms behind the development of the topological surface states in SmB₆ and how the relativistic quasiparticles achieve thermal equilibrium remains a scientific challenge. In this study, we delve into the intricate behaviors of SmB₆, with a focus on the intermediate temperature region (5-15 K) where topological surface states begin to develop whereas the bulk is already a gapped insulator. Most notably, we observed stable electrical voltage and current between two electrodes placed on different surface regions of SmB₆, which persist over macroscopic timescales. Moreover, our investigation reveals a strong connection between the spontaneous surface potential and the presence of topological surface states. Thus, we infer that the formation of localized inhomogeneity of topological surface states at intermediate temperature range underlies this intriguing behavior. Our observations not only reveal a novel electrical transport behavior in SmB₆ but also demonstrate the potential of SmB₆ as a platform for converting thermal energy from the environment into electrical energy.