Chiral Spin Waves in a Dirac Fermi-Liquid with Spin-Orbit Coupling

Spin-orbit coupling (SOC) allows an external electric field to manipulate spins directly through the electron-dipole spin resonance (EDSR). This is particularly useful in characterizing the dynamics of spins in low-dimensional systems with a smaller number of carriers. In this work, we study the EDSR response of a 2D Dirac Fermi-Liquid (FL) with extrinsic SOC, e.g., graphene adsorbed on a transition metal dichalcogenide, and analyze the behavior of the uniform (q=0) collective spin excitations of the system – chiral spin waves – as they evolve with a static in-plane magnetic field. Treating the external effects as weak perturbations, the phenomenological FL theory (extended to a multi-valley system) can be used to describe the structure of the modes as well as obtain the resonant contributions to the optical conductivity.