Nonlinear density response theory is revisited focusing on the harmonically perturbed finite temperature uniform electron gas. Within the non-interacting limit, brute force quantum kinetic theory calculations for the quadratic, cubic, quartic and quintic responses reveal a deep connection with the linear response. Careful analysis of the static long wavelength limit led us to conjecture a canonical non-interacting form that expresses arbitrary order nonlinear responses as the weighted sum of the linear responses evaluated at all multiple harmonics. This harmonic expansion is successfully validated against ab initio path integral Monte Carlo simulations.
EPL (Europhysics Letters)
- Pub Date:
- May 2023
- Condensed Matter - Quantum Gases;
- Condensed Matter - Statistical Mechanics;
- Physics - Plasma Physics
- 7 pages, 3 figures, 169 pages of supplementary material