Cavity-Induced Excitonic Insulation and Non-Fermi-Liquid Behavior in Dirac Materials

TL;DR

This paper explores how high-impedance metasurface cavities can induce novel quantum phases in 2D Dirac fermions, including excitonic insulators and non-Fermi-liquid behavior, by mediating long-range interactions.

Contribution

It demonstrates that engineered cavity interactions can qualitatively change the ground state of Dirac materials, inducing phase transitions and non-Fermi-liquid regimes.

Findings

For N_f < 16/π, an excitonic insulating phase emerges with a mass gap.

For N_f > 16/π, the system exhibits a non-Fermi-liquid critical regime with suppressed quasiparticle residue.

Cavity fluctuations lift Landau level degeneracy under magnetic fields across all N_f.

Abstract

We investigate two-dimensional Dirac fermions embedded in a deep-subwavelength cavity formed by high-impedance metasurfaces. We point out that, unlike conventional metallic boundaries, these metasurfaces support quasielectrostatic transverse-magnetic modes that mediate a long-range interaction between two-dimensional electrons. Combining static electronic screening with a Dyson-Schwinger analysis, we show that this engineered interaction can qualitatively alter the ground-state properties of Dirac materials. For a fermion flavor number $N_{f}$ below a critical value $N_{c}=16/\pi$, the interaction drives an excitonic insulating phase through an infinite-order quantum phase transition and spontaneously generates a mass gap. At $N_{f}>N_{c}$, the system remains gapless but enters a non-Fermi-liquid critical regime where the quasiparticle residue is singularly suppressed to zero, and the Dirac cone exhibits a nonanalytic dispersion relation. Furthermore, under a perpendicular magnetic field, the cavity fluctuations dynamically lift the zeroth Landau level degeneracy across all $N_{f}$. These results identify high-impedance metasurface cavities as promising platforms for engineering correlated Dirac matter.