BACK-FLOW ELECTRIC-CURRENT - DC CURRENT AS A QUADRATIC RESPONSE TO AN AC FIELD

We study an interaction of a running longitudinal wave with a metal. It is shown within a quadratic response that a single wave creates a dc electric current even if the creation of electron-hole pairs is prohibited. As a consequence, a macroscopic electric current depends on an instant distribution of bosons, e.g., plasmons. Beside a formal theory, two practical formulas are provided: the random phase approximation formula for a general electron band structure, and a general formula for a single parabolic band. © 1994 The American Physical Society.