Energy-Efficient Sub-Terahertz Photoresponse via Sublattice Magnetic Transition

Abstract

The proliferation of ambient electromagnetic radiation with the explosion of Internet of Things, 6G communication and millimeter-wave systems calls for the development of broadband, scalable detectors operating under ultralow-power conditions. Here, we demonstrate a high-performance, self-driven THz photodetector based on the van der Waals ferromagnetic metal Fe₅GeTe₂. It is elucidated that the room-temperature optoelectronic response is predominantly driven by the photothermoelectric (PTE) effect under zero-bias conditions. The device achieves stable broadband detection (0.02–0.3 THz), an ultrafast response time of 0.83 μs, and excellent linear power dependence. Especially, we reveal the intriguing optoelectronic behavior with significant enlargement of magnitude driven by the intrinsic magnetic phase transition-specifically the magnetic ordering of the Fe1 sublattice below 121 K within the already ferromagnetic matrix. As the temperature drops below 121 K, this localized sublattice magnetic transition significantly facilitates the directional transport of photogenerated carriers, translating into a substantially augmented photoresponse. Furthermore, leveraging this fundamental process of magnetic phase-transition as well as the suppressed thermal noise, the intermediate-frequency (IF) signal intensity in heterodyne mixing is remarkably enhanced by the long-range magnetic-ordering, and remains almost unchanged near room temperature. Utilizing these exceptional capabilities, we successfully constructed a point-to-point communication link for the data-transmission of bit-streams and images. This work provides a novel strategy for a highly integrated, low-power platform for future high-signal-to-noise-ratio wireless harvester, broadband detection.