Anisotropic photocurrent response at MnBi₂Te₄-metal interface

The magnetic topological insulator MnBi2Te4 has attracted a lot of research interests for its exotic properties due to the interplay between nontrivial topology and magnetism. Here, we report the photocurrent (PC) response of MnBi2Te4 flakes under the excitation wavelengths between 633 nm and 4000 nm measured by scanning PC microscopy. We observe a significant polarization dependent PC response at the interface between metal electrode and MnBi2Te4, while the PC response remains polarization-independent at MnBi2Te4 layer steps. The polarization dependent PC at the MnBi2Te4-metal electrode interface, which is attributed to the polarization dependent light absorption at the interface, preserves in the whole tested wavelength range. The responsivity of the device is 80 μA W-1. This responsivity as well as PC polarity is consistent with the results calculated based on a photo-thermoelectric generation mechanism, thus we infer that photo-thermoelectric effect dominates in the PC generation at MnBi2Te4-metal interface. Our results reveal the photoelectric response mechanism of the emerging material MnBi2Te4 for its potential optoelectronic applications.