Impurity Screening and Friedel Oscillations in Floquet-driven Two-dimensional Metals

TL;DR

This paper develops a theory for how strong periodic driving affects impurity screening and Friedel oscillations in two-dimensional metals, revealing tunable oscillation patterns and regimes of screening suppression.

Contribution

It introduces a comprehensive non-equilibrium screening theory for Floquet-driven 2D metals, highlighting the emergence of multiple Friedel oscillation periods and the suppression of screening under strong drives.

Findings

Weak drive regime shows unconventional Friedel oscillations with multiple periods.

Strong drive regime results in almost unscreened impurity potential.

Dynamic driving field enables tunable impurity screening properties.

Abstract

We develop a theory for the non-equilibrium screening of a charged impurity in a two-dimensional electron system under a strong time-periodic drive. Our analysis of the time-averaged polarization function and dielectric function reveals that Floquet driving modifies the screened impurity potential in two main regimes. In the weak drive regime, the time-averaged screened potential exhibits unconventional Friedel oscillations with multiple spatial periods contributed by a principal period modulated by higher-order periods, which are due to the emergence of additional Kohn anomalies in the polarization function. In the strong drive regime, the time-averaged impurity potential becomes almost unscreened and does not exhibit Friedel oscillations. This tunable Friedel oscillations is a result of the dynamic gating effect of the time-dependent driving field on the two-dimensional electron system.