Twist-Tunable Interlayer Excitons in Anisotropic ReS 2 /ReSe 2 Heterostructures

Interlayer excitons (IEs) in van der Waals heterostructures offer tunable excitonic states with long lifetimes and permanent dipole moments. Prior studies focused on isotropic 2H-phase transition metal dichalcogenides, where bright IE emission is confined near high-symmetry twist angles (0° and 60°), restricting tunability. Here, heterobilayers of monolayer ReS2 and ReSe2, both in the 1T′ phase, exhibit robust polarized IE emission near 1.2 eV across the full twist-angle range (1°–88°), reflecting a hybridization landscape governed by lattice anisotropy rather than valley alignment. The lowest-energy IE transition exhibits a nonmonotonic twist-angle dependence with a total modulation range of ∼60 meV, consistent with moiré-driven band renormalization and modulation of interlayer coupling revealed by first-principles calculations and low-frequency Raman spectroscopy, respectively. Overall IE energy tunability extends to ∼100 meV with multilayer ReS2 and excitation energy variation. These results establish ReS2/ReSe2 as a versatile infrared IE platform enabling polarization-resolved emitters and detectors beyond 2H-symmetry constraints.