Instability of Anisotropic Fermi Surfaces in Two Dimensions

TL;DR

This paper investigates how strong anisotropy affects the Fermi surface in two-dimensional correlated electron systems, revealing enhanced instabilities and a shift in the critical dimension for non-Fermi liquid behavior, with implications for superconducting symmetry.

Contribution

It introduces a renormalization group analysis of anisotropic Fermi surfaces, showing how inflection points influence instabilities and the nature of superconducting order.

Findings

Inflection points alter scaling exponents and enhance system instabilities.

Critical dimension for non-Fermi liquid behavior increases from 1 to 3/2.

Provides rules to distinguish between d-wave and extended s-wave superconducting states.

Abstract

The effect of strong anisotropy on the Fermi line of a system of correlated electrons is studied in two space dimensions, using renormalization group techniques. Inflection points change the scaling exponents of the couplings, enhancing the instabilities of the system. They increase the critical dimension for non Fermi liquid behavior, from 1 to 3/2. Assuming that, in the absence of nesting, the dominant instability is towards a superconducting ground state, simple rules to discern between d-wave and extended s-wave symmetry of the order parameter are given.