Collective modes and optical response in twisted WSe₂

Over a range of twist angles, twisted WSe₂ displays a superconducting region in proximity to a correlated state (likely an intervalley-coherent (IVC) antiferromagnet (AFM)). We study the particle-hole collective modes of different IVC and valley-polarized (VP) phases within the time-dependent Hartree-Fock approximation. We track the evolution of the collective-mode velocity and gaps as a function of twist angle and dielectric screening. Due to the strong magneto-electric coupling in the IVC-AFM phase, we find a sizable finite-q optical response generated by its spin waves, potentially accessible in near-field or on-chip THz spectroscopy.