Giant Modulation of Interlayer Coupling in Twisted Bilayer ReS ₂

Abstract 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 ₂ can be continuously modulated by the twist angle. By controlling the twist angle between 0° and 10°, the exciton energy of tBL ReS ₂ is tuned over a range of 40 meV, which is comparable to the difference between the exciton energies of intrinsic monolayer and bilayer ReS ₂ . Such a wide modulation range for the interlayer coupling strength of tBL ReS ₂ , 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 ₂ 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 ₂ is attributed to the low symmetry of the 1T ' structure and in‐plane anisotropy of the ReS ₂ lattice. These findings demonstrate the enhanced tunability of twist‐controlled electronic structure in anisotropic 2D materials, offering new pathways for designing reconfigurable quantum materials.