THz detector based on proximity effect of topological insulator

Designing THz detectors that operate at room temperature is highly desirable and challenging for practical applications, such as imaging and quality control. Since the THz photon energy is very close to the thermal excitation, the room temperature operation is very restricted in conventional devices. In contrast, the topological insulators (TIs), e.g. Bi₂Se₃, pave a way to a new paradigm in low energy optoelectronics due to unique electronic properties of surface electrons. In this work, we analyze THz photodetectors based on the proximity effect in the hybrid TI- ferromagnetic insulator (FMI) structure (Fig.1). The predicted photocurrent of the unit cell can reach the order of 10^-7A·cm/W, which is of practical importance. Moreover, the sensitivity of the proposed devices can be extended beyond the thermal limit, since the output signal can be readily distinguishable from the background thermal excitation for signals in THz/far infrared frequency domain even at room temperature.