Tuning the low-energy band structure in twisted bilayer WSe2

TL;DR

This study uses nano-ARPES to systematically investigate how twist angles in bilayer WSe2 affect its low-energy electronic band structure, revealing tunable band separations and implications for device applications.

Contribution

It provides the first detailed analysis of twist-angle-dependent electronic structure evolution in bilayer WSe2 using nano-ARPES.

Findings

The valence band maxima position is independent of twist angle.

The energy separation between hole bands at K and Γ varies by over 100 meV.

Implications for tuning band gaps and spin-dependent electron-phonon interactions.

Abstract

Tuning the electronic structures of two-dimensional (2D) material-based heterostructures is of crucial importance for their use in functional next-generation electronics. Here, through angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nano-ARPES), we systematically track the evolution of the near-Fermi-level electronic structure of bilayer WSe2 over a large range of twist angle. While the momentum positioning of the valence band maxima is independent of twist angle, we find that the energetic separation between the hole bands at the K point of the Brillouin zone and the higher binding-energy hole band at {\Gamma} can be varied in excess of 100 meV. We explore the mechanisms underpinning this evolution and discuss the implications for tuning both the size of the band gaps, and the efficiency of the spin-dependent electron-phonon coupling channels in homobilayer transition metal dichalcogenide devices.