Fermi surface fluctuations and single electron excitations near Pomeranchuk instability in two dimensions

TL;DR

This paper investigates how a Pomeranchuk instability with d-wave symmetry in a two-dimensional electron system causes significant Fermi surface fluctuations, leading to non-Fermi liquid behavior and altered single-electron excitations.

Contribution

It provides a phenomenological analysis of fluctuation effects near a Pomeranchuk quantum critical point, revealing divergence in density correlations and breakdown of Fermi liquid theory.

Findings

Density correlations diverge with dynamical exponent z=3.

Fermi liquid behavior is destroyed over most of the Fermi surface.

Single-particle decay rates exceed excitation energies at low energies.

Abstract

A metallic electron system near an orientational symmetry breaking Pomeranchuk instability is characterized by a ''soft'' Fermi surface with enhanced collective fluctuations. We analyze fluctuation effects in a two-dimensional electron system on a square lattice in the vicinity of a Pomeranchuk instability with d-wave symmetry, using a phenomenological model which includes interactions with a small momentum transfer only. We compute the dynamical density correlations with a d-wave form factor for small momenta and frequencies, the dynamical effective interaction due to fluctuation exchange, and the electron self-energy. At the quantum critical point the density correlations and the dynamical forward scattering interaction diverge with a dynamical exponent z=3. The singular forward scattering leads to large self-energy corrections, which destroy Fermi liquid behavior over the whole Fermi surface except near the Brillouin zone diagonal. The decay rate of single-particle excitations, which is related to the width of the peaks in the spectral function, exceeds the excitation energy in the low-energy limit. The dispersion of maxima in the spectra flattens strongly near those portions of the Fermi surface which are remote from the zone diagonal.