Polarization catastrophe in the polaronic Wigner crystal

TL;DR

This paper investigates the collective excitations of a polaronic Wigner crystal and reveals a polarization catastrophe at high densities, providing optical signatures consistent with experimental observations in Nd-based cuprates.

Contribution

It introduces a theoretical analysis of polarization instability in a polaronic Wigner crystal considering quantum fluctuations, highlighting a novel polarization catastrophe phenomenon.

Findings

Identification of a polarization catastrophe at high electron densities

Derivation of an optical signature of the instability

Agreement with experimental data in Nd-based cuprates

Abstract

We consider a three dimensional Wigner crystal of electrons lying in a host ionic dielectric. Owing to their interaction with the lattice polarization, each localized electron forms a polaron. We study the collective excitations of such a polaronic Wigner crystal at zero temperature, taking into account the quantum fluctuations of the polarization within the Feynman harmonic approximation. We show that, contrary to the ordinary electron crystal, the system undergoes a polarization catastrophe when the density is increased. An optical signature of this instability is derived, whose trend agrees with the experiments carried out in Nd-based cuprates.