Metallic phase in a two-dimensional disordered Fermi system with singular interactions

TL;DR

This paper investigates a disordered 2D fermion system with singular gauge interactions, revealing unique quantum corrections to conductivity and demonstrating the system's robustness as a metal at low temperatures.

Contribution

It introduces a detailed analysis of quantum corrections and dephasing mechanisms in a disordered fermion system with singular gauge interactions, highlighting differences from conventional Fermi liquids.

Findings

Weak localization is suppressed by magnetic field fluctuations.

Quantum fluctuations induce dephasing proportional to the loop perimeter.

The system remains metallic at low temperatures despite singular interactions.

Abstract

We consider a disordered system of gapless fermions interacting with a singular transverse (2+1)-dimensional gauge-field. We study quantum corrections to fermion conductivity and show that they are very different from those in a Fermi liquid with non-singular interactions. In particular, the weak-localization effect is suppressed by magnetic field fluctuations. We argue that these fluctuations can be considered static at time scales of fermionic diffusion. By inducing fluxes through diffusive loops that contribute to weak localization, they dephase via the Aharonov-Bohm effect. It is shown that while the flux-flux correlator due to thermal fluctuations of magnetic field is proportional to the area enclosed by the loop, the correlator due to quantum fluctuations is proportional to the perimeter of the loop. The possibility of dephasing due to these quasistatic configurations and the corresponding rates are discussed. We also study interaction induced effects and show that perturbation theory contains infrared divergent terms originating from unscreened magnetic interactions. These singular (Hartree) terms are related to scattering of a fermion off of the static potential created by the other fermions. We show that due to singular small-angle scattering, the corresponding contributions to the density of states and conductivity are very large and positive indicating that the fermion-gauge system remains metallic at low temperatures.