Dynamical response of a weakly pinned two-dimensional Wigner crystal

TL;DR

This paper investigates how a weakly pinned two-dimensional Wigner crystal responds to AC electric fields, revealing a disorder and magnetic field-dependent resonance that is sharp in strong magnetic fields due to Coulomb interactions.

Contribution

It provides a detailed analysis of the dynamical response of a 2D Wigner crystal, highlighting the emergence of a sharp resonance in strong magnetic fields linked to Coulomb interactions.

Findings

Inhomogeneously broadened absorption line appears at frequency ω_p.

Line sharpness increases with magnetic field strength.

Resonance width relates to the density of states in the phonon spectrum.

Abstract

Motivated by puzzling results of recent experiments, we re-examine the response of a weakly pinned two-dimensional Wigner crystal to a uniform AC electric field. We confirm that at some disorder and magnetic field dependent frequency $\omega_p$, an inhomogeneously broadened absorption line emerges. Although the line is conventionally broad in zero magnetic field, in strong fields it appears as a sharp resonance whose width is related to the density of states in the low-frequency tail of the zero-field phonon spectrum. This behavior originates due to the long-range Coulomb interactions.