Photogalvanic spectroscopy on MnBi₂Te₄ topological insulator thin films

We demonstrate zero-bias mid-infrared photocurrent generation in topological insulator MnBi2Te4 thin films. The symmetry breakings at the surface and interfaces lead to the coexistence of Dirac and Rashba band states, which enable two kinds of photogalvanic responses. One is the magneto-photogalvanic effect in the presence of an external in-plane magnetic field perpendicular to photocurrent direction, and the other is the light-polarization-dependent linear photogalvanic effect arising from in-plane symmetry breakings, both observed up to room temperature. We disentangle these contributions by light-polarization and temperature dependent spectroscopy under the varying magnetic field.