Zero-bias photocurrent in ferromagnetic topological insulator.

N. Ogawa,M. Kawasaki,Y. Tokura,R. Yoshimi,K. Yasuda,A. Tsukazaki

doi:10.1038/ncomms12246

Abstract

Magnetic interactions in topological insulators cause essential modifications in the originally mass-less surface states. They offer a mass gap at the Dirac point and/or largely deform the energy dispersion, providing a new path towards exotic physics and applications to realize dissipation-less electronics. The nonequilibrium electron dynamics at these modified Dirac states unveil additional functions, such as highly efficient photon to spin-current conversion. Here we demonstrate the generation of large zero-bias photocurrent in magnetic topological insulator thin films on mid-infrared photoexcitation, pointing to the controllable band asymmetry in the momentum space. The photocurrent spectra with a maximal response to the intra-Dirac-band excitations can be a sensitive measure for the correlation between Dirac electrons and magnetic moments.

Highlights

Magnetic interactions in topological insulators cause essential modifications in the originally mass-less surface states
Bismuth-chalcogenides-based topological insulators[1] (TIs) generally have the bulk band gap of several hundreds meV, where the conduction and valence bands are connected by the surface states: mass-less Dirac dispersions with spinmomentum locking
We study photocurrent spectra in Cr0.3(Bi0.22Sb0.78)1.7Te3 (CBST) thin films with a thickness of 8 nm

Summary

Introduction

Magnetic interactions in topological insulators cause essential modifications in the originally mass-less surface states. For the case of in-plane magnetization, for example, the finite Sy, the gap closes or substantially reduces, with the Dirac point shifted from the zone center along kx due to the Zeeman effect (Fig. 1a). We show the generation of large zero-bias photocurrent on mid-infrared photoexcitation at normal incidence (Fig. 1b), realized by the field-controllable band asymmetry in the momentum space.

Results

Conclusion