Collinear scattering and long-lived excitations in two-dimensional electron fluids

TL;DR

This paper demonstrates the existence of long-lived excitations in 2D Fermi gases due to collinear quasiparticle scattering, exceeding traditional lifetime bounds and linked to supersymmetric zero modes.

Contribution

It provides a direct calculation showing these excitations and connects their longevity to a supersymmetric quantum mechanical framework.

Findings

Excitations have lifetimes exceeding Landau Fermi-liquid bounds by a factor of (TF/T)^α.

Long-lived excitations are associated with Fermi-surface modulations of odd parity.

Identifies zero modes as supersymmetric solutions in a quantum kinetic framework.

Abstract

For a long time, it has been thought that 2D Fermi gases could support long-lived excitations, thanks to the collinear quasiparticle scattering controlled by phase space constraints at a 2D Fermi surface. We present a direct calculation that reveals such excitations. The excitation lifetimes are found to exceed the fundamental bound set by Landau Fermi-liquid theory by a factor as large as $(T_F/T)^\alpha$ with $\alpha \approx 2$. These excitations represent Fermi-surface modulations of an odd parity, one per each odd angular momentum. To explain this surprising behavior, we employ a connection between the linearized quantum kinetic equation and the dynamics of a fictitious quantum particle moving in a 1D reflectionless ${\rm sech^2}$ potential. In this framework, we identify the long-lived excitations in Fermi gases as zero modes that arise from supersymmetry.