Control of Subband Energies via Interlayer Twisting in an Artificially Stacked WSe2 Bilayer.

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 WSe2/h-BN/twisted bilayer (tBL) WSe2 devices with a wide range of twist angles (θBL) of tBL WSe2, 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 WSe2. The subband separation, which directly measured the interlayer coupling strength, was tuned by ∼0.1 eV as θBL increased toward 6° and remained nearly constant for larger θBL values. The θBL dependence was attributed to the emergence of a stable W/Se (Se/W) stacking domain in the small θBL region, owing to the atomic reconstruction of the moiré lattice in tBL WSe2. Our findings demonstrate that the twist-controlled subband energies in tBL WSe2 are predominantly determined by local atomic reconstruction.