Terahertz Photodetection with Type-II Dirac Fermions in Transition-Metal Ditellurides and Their Heterostructures

Transition-metal dichalcogenides PtTe2, PdTe2, and NiTe2 deserve particular attention, due to the presence of type-II Dirac fermions. As a matter of fact, tilted Dirac cones afford a suitable platform for optoelectronics of dissipation-less carrier-transport, favored by their ultrahigh carrier mobility, and large nonsaturating magnetoresistance. Herein, it is shown that PtTe2, PdTe2, and NiTe2 display high-speed terahertz (THz) detection capability at room temperature, which originates from their peculiar band structure with topologically protected electronic states. Furthermore, photodetectors based on their heterostructures are able to suppress dark current with high-performance detection of THz light. Furthermore, these crystals are stable in air and they can be easily exfoliated in nanosheets by liquid-phase exfoliation, due to the weak interlayer van der Waals bonds. The obtained results clearly establish that the type-II Dirac semimetals based on transition-metal ditellurides have immense research potential for addressing application-oriented issues for remote sensing and telecommunications.