Shift charge and spin photocurrents in Dirac surface states of topological insulator

TL;DR

This paper demonstrates that Dirac surface states in topological insulators can generate shift charge and spin photocurrents under linearly polarized light, with potential applications in optoelectronics.

Contribution

It reveals the generation of shift charge and spin photocurrents in topological insulator surface states, including the effect of hexagonal warping and time-reversal symmetry breaking.

Findings

Shift charge current magnitude is approximately 0.13 times the light intensity $I_0$.

Shift spin-current magnitude is approximately 0.21 times $I_0$ (nA/m).

Dirac surface states can efficiently produce photocurrents under linearly polarized light.

Abstract

The generation of photocurrent in condensed matter is of main interest for photovoltaic and optoelectronic applications. Shift current, a nonlinear photoresponse, has attracted recent intensive attention as a dominant player of bulk photovoltaic effect in ferroelectric materials. In three dimensional topological insulators $\text{Bi}_2\text{X}_3$ (X: Te, Se), we find that Dirac surface states with a hexagonal warping term carry shift current by linearly polarized light. In addition, shift spin-current is introduced with the time-reversal symmetry breaking perturbation. The estimate for the magnitudes of the shift charge- and spin-currents are 0.13$I_0$ and 0.21$I_0$(nA/m) with the intensity of light $I_0$ measured in $(\text{W}/\text{m}^2)$, respectively, which can offer a useful method to generate these currents efficiently.