Dispersion Instability in Strongly Interacting Electron Liquids

TL;DR

This paper investigates how strongly interacting, low-density electron liquids can develop a dispersion instability characterized by diverging effective mass and negative quasiparticle velocity, affecting their physical properties.

Contribution

It reveals the occurrence of dispersion instability in low-density electron liquids due to long-range Coulomb interactions, highlighting the role of soft plasmon emission.

Findings

Dispersion instability occurs at a critical density with diverging effective mass.

The instability manifests away from the Fermi momentum at higher densities.

Both 2D and 3D electron liquids exhibit this instability.

Abstract

We show that the low-density strongly interacting electron liquid, interacting via the long-range Coulomb interaction, could develop a dispersion instability at a critical density associated with the approximate flattening of the quasiparticle energy dispersion. At the critical density the quasiparticle effective mass diverges at the Fermi surface, but the signature of this Fermi surface instability manifests itself away from the Fermi momentum at higher densities. For densities below the critical density the system is unstable since the quasiparticle velocity becomes negative. We show that one physical mechanism underlying the dispersion instability is the emission of soft plasmons by the quasiparticles. The dispersion instability occurs both in two and three dimensional electron liquids. We discuss the implications of the dispersion instability for experiments at low electron densities.