High-field charge transport on the surface of Bi$_2$Se$_3$

TL;DR

This paper presents a theoretical model explaining high-field surface charge transport in Bi$_2$Se$_3$, reproducing experimental features like incomplete current saturation and residual conductance through hot-electron effects and carrier excitation.

Contribution

The study provides a comprehensive theoretical explanation for high-field surface transport phenomena in Bi$_2$Se$_3$, aligning with experimental observations without invoking bulk contributions.

Findings

Conductance decreases due to hot-electron effects

Electric field excites carriers, increasing conductance

Finite residual conductance observed at high fields

Abstract

We present a theoretical study on the high-field charge transport on the surface of Bi$_2$Se$_3$ and reproduce all the main features of the recent experimental results, i.e., the incomplete current saturation and the finite residual conductance in the high applied field regime [Costache {\it et al.}, Phys. Rev. Lett. {\bf 112}, 086601 (2014)]. Due to the hot-electron effect, the conductance decreases and the current shows the tendency of the saturation with the increase of the applied electric field. Moreover, the electric field can excite carriers within the surface bands through interband precession and leads to a higher conductance. As a joint effect of the hot-electron transport and the carrier excitation, the conductance approaches a finite residual value in the high-field regime and the current saturation becomes incomplete. We thus demonstrate that, contrary to the conjecture in the literature, the observed transport phenomena can be understood qualitatively in the framework of surface transport alone. Furthermore, if a constant bulk conductance which is insensitive to the field is introduced, one can obtain a good quantitative agreement between the theoretical results and the experimental data.