Non-Fermi-Liquid Behavior from Cavity Electromagnetic Vacuum Fluctuations at the Superradiant Transition

TL;DR

This paper investigates how electromagnetic vacuum fluctuations in a cavity can induce non-Fermi-liquid behavior in two-dimensional materials at the superradiant transition, with effects depending on lattice geometry.

Contribution

It reveals that cavity-induced electromagnetic fluctuations can lead to non-Fermi-liquid behavior near the superradiant transition, highlighting the role of lattice structure in this phenomenon.

Findings

In square lattices, quasiparticles are preserved due to limited electron-photon scattering.

In honeycomb lattices, quasiparticles are destroyed by overdamped electromagnetic modes.

Cavity probes can measure the electromagnetic mode spectrum responsible for non-Fermi-liquid behavior.

Abstract

We study two-dimensional materials where electrons are coupled to the vacuum electromagnetic field of a cavity. We show that, at the onset of the superradiant phase transition towards a macroscopic photon occupation of the cavity, the critical electromagnetic fluctuations, consisting of photons strongly overdamped by their interaction with electrons, can in turn lead to the absence of electronic quasiparticles. Since transverse photons couple to the electronic current, the appearance of non-Fermi-Liquid behavior strongly depends on the lattice. In particular, we find that in a square lattice the phase space for electron-photon scattering is reduced in such a way to preserve the quasiparticles, while in a honeycomb lattice the latter are removed due to a non-analytical frequency dependence of the damping $\propto |\omega|^{2/3}$. Standard cavity probes could allow to measure the characteristic frequency spectrum of the overdamped critical electromagnetic modes responsible for the non-Fermi-liquid behavior.