Direct Measurement of Terahertz Conductivity in a Gated Monolayer Semiconductor.

Chen, Su-Di; Feng, Qixin; Zhao, Wenyu; Qi, Ruishi; Zhang, Zuocheng; Abeysinghe, Dishan; Uzundal, Can; Xie, Jingxu et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Two-dimensional semiconductors and their moiré superlattices have emerged as important platforms for investigating correlated electrons. However, many key properties of these systems, such as the frequency-dependent conductivity, remain experimentally inaccessible because of the mesoscopic sample size. Here we report a technique to directly measure the complex conductivity of electrostatically gated two-dimensional semiconductors in the terahertz frequency range. Applying this technique to a WSe<sub>2</sub> monolayer encapsulated in hBN, we observe a clear Drude-like response between 0.1 and 1 THz, in a density range challenging to access even in DC transport. Our work opens a new avenue for studying tunable van der Waals heterostructures using terahertz spectroscopy.