Giant room-temperature terahertz photothermoelectric response mediated by hot carriers at the metal-semimetal interfaces

The hot-carrier photothermoelectric (PTE) effect in two-dimensional materials can be used to develop room-temperature, fast, and sensitive detectors for microwave, terahertz, and far-infrared radiations. Here, we present a van der Waals semimetal PtSe₂ terahertz detector and find a giant terahertz PTE response mediated by hot carriers at the metal-PtSe₂ interfaces. The detector demonstrates an excellent zero-bias responsivity of 0.62 ampere per watt (A/W), a low-noise equivalent power of 19.6 picowatt per square root of hertz (pW/Hz^1/2), and a fast response time of 4.5 nanosecond (ns) at 0.1 terahertz (THz). The metal doping effect and asymmetric terahertz heating play vital roles in the hot-carrier PTE response at the metal-semimetal interfaces. Moreover, scanning photocurrent mapping shows that the short-wave zero-bias photoresponse is closely localized to the metal-semimetal interfaces, further revealing the metal doping effect. The bias-dependent photocurrent indicates that the short-wave photoresponse still originates from the PTE effect and the photovoltaic response is negligible. Our results provide important guidance for developing high performance semimetal detectors.