Ultrasensitive Anisotropic Room-Temperature Terahertz Photodetector Based on an Intrinsic Magnetic Topological Insulator MnBi2Te4.

Terahertz photodetectors based on emergent intrinsic magnetic topological insulators promise excellent performance in terms of highly sensitive, anisotropic and room-temperature ability benefiting from their extraordinary material properties. Here, we propose and conceive the response features of exfoliated MnBi2Te4 flakes as active materials for terahertz detectors. The MnBi2Te4-based photodetectors show the sensitivity rival with commercially available ones, and the noise equivalent power of 13 pW/Hz0.5 under 0.275 THz at room-temperature led by the nonlinear Hall effect, allowing for the high-resolution terahertz imaging. In addition, a large anisotropy of polarization-dependent terahertz response is observed when the MnBi2Te4 device is tuned into different directions. More interestingly, we discover an unprecedented power-controlled reversal of terahertz response in the MnBi2Te4-graphene device. Our results provide feasibility of manipulating and exploiting the nontrivial topological phenomena of MnBi2Te4 under a high-frequency electromagnetic field, representing the first step toward device implementation of intrinsic magnetic topological insulators.