Control of Subband Energies via Interlayer Twisting in an Artificially Stacked WSe<sub>2</sub> Bilayer.

Kinoshita, Kei; Moriya, Rai; Okazaki, Shota; Onodera, Momoko; Zhang, Yijin; Watanabe, Kenji; Taniguchi, Takashi; Sasagawa, Takao et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

Tuning the electronic structure of artificially stacked bilayer crystals using their twist angle has attracted a significant amount of interest. In this study, resonant tunneling spectroscopy was performed on trilayer WSe<sub>2</sub>/<i>h</i>-BN/twisted bilayer (tBL) WSe<sub>2</sub> devices with a wide range of twist angles (θ<sub>BL</sub>) of tBL WSe<sub>2</sub>, from 0° to 34°. We observed two resonant tunneling peaks, identified as the first and second lowest hole subbands at the valence band Γ point of tBL WSe<sub>2</sub>. The subband separation, which directly measured the interlayer coupling strength, was tuned by ∼0.1 eV as θ<sub>BL</sub> increased toward 6° and remained nearly constant for larger θ<sub>BL</sub> values. The θ<sub>BL</sub> dependence was attributed to the emergence of a stable W/Se (Se/W) stacking domain in the small θ<sub>BL</sub> region, owing to the atomic reconstruction of the moiré lattice in tBL WSe<sub>2</sub>. Our findings demonstrate that the twist-controlled subband energies in tBL WSe<sub>2</sub> are predominantly determined by local atomic reconstruction.