Terahertz response of monolayer and few-layer WTe2 at the nanoscale

THz near-field nano-imaging

We investigated multi-terraced microcrystals of WTe2 using a home-built apparatus enabling nano-THz experiments at cryogenic temperature23. The THz beam is focused onto an AFM tip with an (80) µm long shaft made of PtIr wire. The tip apex locally confines and enhances the THz electric field. The tip shaft functions as an antenna35 and out-couples the near-field radiation into far-field radiation reaching the photoconductive antenna (PCA) detector. The tapping of the tip modulates the near-field signal at ~70 kHz. We demodulated the amplitude of the tip-scattered electric field at the first (({S}_{1})) and the second (({S}_{2})) harmonics of the tip tapping frequency to suppress the undesired far-field background23,36.

The exfoliated micro-crystals of…

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