Helicity-Resolved Non-resonant/Resonant Raman Responses of WSe₂/MoS₂ Heterostructures under External Magnetic Fields

Helicity-resolved (HR) Raman scattering serves as a direct probe of phonon symmetry, spin–valley locking, and intervalley scattering mechanisms in two-dimensional semiconductors. Different phonon modes exhibit distinct helicity behaviors depending on their symmetry and coupling to electronic states. This helicity dependence provides insights into spin–valley interactions and how lattice vibrations couple to valley-polarized carriers. Here, we employ a 633 nm excitation laser to resonantly enhance Raman modes in MoS₂, while simultaneously extracting off-resonant Raman features from stacking-angle-aligned WSe₂ for comparison. The valley-dependent phonon coupling is revealed through HR Raman measurements under external magnetic fields ranging from 0 to 9 T at both 2.5 K and 295 K. In addition to the field-dependent intensity extrema observed at 2.5 K, we report all resonant phonon HR responses of MoS₂ at 295 K to further elucidate the thermal effects on magneto-Raman intensities. This study highlights the spin- and valley-dependent exciton–phonon coupling mechanisms and underscores their critical role in the design of future opto-spintronic devices, where valley-dependent phonon scattering governs device performance.