Terahertz fingerprint of monolayer Wigner crystals

TL;DR

This paper predicts that monolayer Wigner crystals can be detected via their unique terahertz response spectrum, revealing internal optical transitions and shifts with charge density, providing a new spectroscopic signature for these quantum states.

Contribution

It introduces a theoretical framework to identify monolayer Wigner crystals through their terahertz spectra, including internal quantum structure and density-dependent peak shifts.

Findings

Terahertz spectra exhibit characteristic multi-peak structures.

Peak positions shift systematically with charge density.

Results applicable to various two-dimensional materials.

Abstract

The strong Coulomb interaction in monolayer semiconductors represents a unique opportunity for the realization of Wigner crystals without external magnetic fields. In this work, we predict that the formation of monolayer Wigner crystals can be detected by their terahertz response spectrum, which exhibits a characteristic sequence of internal optical transitions. We apply the density matrix formalism to derive the internal quantum structure and the optical conductivity of the Wigner crystal and to microscopically analyze the multi-peak shape of the obtained terahertz spectrum. Moreover, we predict a characteristic shift of the peak position as function of charge density for different atomically thin materials and show how our results can be generalized to an arbitrary two-dimensional system.