Nonlocal optical conductivity of Fermi surface nesting materials

We use density function theory (DFT) to calculate the band structure and Fermi surface of two dimensional materials, 1T-VSe2 and g-C4N3. We find (part of) the Fermi surface is connected by a nesting vector. We calculate the real part of the inter-band optical conductivity through the imaginary part of the dielectric function. We then use the parabolic band approximation to calculate the nonlocal optical conductivity based on the two particle Green's function approach. We find the Drude peak is shifted to higher frequency and splits into two peaks, which we attribute to two Fermi velocities in the half-metal or spin-valley half metal states. The nonlocal optical conductivity contains relevant information in the electron fluids that is not accessible by standard optical probes. The software we use is DS-PAW (Device studio-projector augmented wave) developed by Hongzhiwei Technology (Shanghai) Co. Ltd. The Perdew-Burke-Ernzerhof (PBE) exchange-correlation energy functional within the generalized gradient approx imation (GGA) were employed.