Giant Modulation of Interlayer Coupling in Twisted Bilayer ReS.

Stacking monolayers of two-dimensional (2D) transition metal dichalcogenides with different twist angles can provide a way to tune their quantum optical and electronic characteristics. This study demonstrates that the bandgap energy and interlayer coupling strength of twisted bilayer (tBL) ReS can be continuously modulated by the twist angle. By controlling the twist angle between 0° and 10°, the exciton energy of tBL ReS is tuned over a range of 40 meV, which is comparable to the difference between the exciton energies of intrinsic monolayer and bilayer ReS. Such a wide modulation range for the interlayer coupling strength of tBL ReS, which significantly affects the band structure, is also shown by the systematic shift in the low-and high-frequency Raman modes and results of a strain study using scanning transmission electron microscopy imaging. Density functional theory calculations on moiré superlattice tBL ReS structures confirm a consistent increase in the bandgap with the twist angle. The strong modulation of interlayer coupling by the twist angle in tBL ReS is attributed to the low symmetry of the 1T' structure and in-plane anisotropy of the ReS lattice. These findings demonstrate the enhanced tunability of twist-controlled electronic structure in anisotropic 2D materials, offering new pathways for designing reconfigurable quantum materials.