Ultrasensitive Anisotropic Room-Temperature Terahertz Photodetector Based on an Intrinsic Magnetic Topological Insulator MnBi 2 Te 4 .

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 MnBi 2 Te 4 flakes as active materials for terahertz detectors. The MnBi 2 Te 4 -based photodetectors show the sensitivity rival with commercially available ones, and the noise equivalent power of 13 pW/Hz 0.5 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 MnBi 2 Te 4 device is tuned into different directions. More interestingly, we discover an unprecedented power-controlled reversal of terahertz response in the MnBi 2 Te 4 -graphene device. Our results provide feasibility of manipulating and exploiting the nontrivial topological phenomena of MnBi 2 Te 4 under a high-frequency electromagnetic field, representing the first step toward device implementation of intrinsic magnetic topological insulators.