Third-order optical conductivity of an electron fluid
Open Access Publications from the University of California

## Third-order optical conductivity of an electron fluid

• Author(s): Sun, Zhiyuan
• Basov, DN
• Fogler, MM
• et al.

## Published Web Location

https://doi.org/10.1103/PhysRevB.97.075432
Abstract

We derive the nonlinear optical conductivity of an isotropic electron fluid at frequencies below the interparticle collision rate. In this regime, governed by hydrodynamics, the conductivity acquires a universal form at any temperature, chemical potential, and spatial dimension. We show that the nonlinear response of the fluid to a uniform field is dominated by the third-order conductivity tensor $\sigma^{(3)}$ whose magnitude and temperature dependence differ qualitatively from those in the conventional kinetic regime of higher frequencies. We obtain explicit formulas for $\sigma^{(3)}$ for Dirac materials such as graphene and Weyl semimetals. We make predictions for the third-harmonic generation, renormalization of the collective-mode spectrum, and the third-order circular magnetic birefringence experiments.

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