On a Connection Between Nonlinear Response to an External Field and Equilibrium Properties of Systems with Interaction: Comment on cond-mat/9711226 by Kopietz and Voelker

TL;DR

This paper warns against naive assumptions linking nonlinear response coefficients to equilibrium properties, illustrating with examples involving mesoscopic electron systems and their response to external fields.

Contribution

It highlights the potential pitfalls in equating kinetic response coefficients with equilibrium quantities, emphasizing the need for careful analysis in mesoscopic systems.

Findings

Naive identification of response and equilibrium coefficients can be misleading

Direct current generation by AC fields differs from equilibrium persistent currents

Interaction effects significantly influence response behavior

Abstract

We demonstrate the danger of a naive identification of kinetic coefficients in the free-electron response expansion in powers of an external electric field and coefficients in the expansion of the corresponding equilibrium quantity in powers of the fluctuating intrinsic electric field. A particular example of the direct current generation by an AC electric field in a mesoscopic system of non-interacting electrons vs. the Fock contribution to the equilibrium persistent current in a system of interacting electrons is considered.