Nonlocal optical conductivity of Fermi surface nesting materials

We investigate the nonlocal optical conductivity of Fermi surface nesting materials that support charge density waves (CDWs) or spin density waves (SDWs). The nonlocal optical conductivity contains information on correlations in electron fluids, which could not be accessed by standard optical probes. A half-metal emerges from doping a CDW, and similarly, a spin-valley half-metal emerges from doping an SDW. Based on the parabolic band approximation, we find that the Drude peak is shifted to a higher frequency and splits into two peaks in the nonlocal optical conductivity. We attribute this to the two Fermi velocities in the half-metal or spin-valley half-metal states.