Competition between different order parameters in a quasi-one-dimensional superconductor

TL;DR

This paper explores the phase diagram of quasi-one-dimensional repulsive Fermi systems, revealing competing density wave and superconducting phases with non-universal order parameter symmetries sensitive to microscopic details.

Contribution

It identifies three potential stable superconducting states and discusses the complexity of predicting their symmetry in real materials due to competing phases.

Findings

Phase diagram includes density wave and superconductivity.

Superconducting order parameter symmetry is non-universal.

Three stable superconducting states: triplet f-wave, singlet d_{x^2-y^2}-wave, d_{xy}-wave.

Abstract

We show that, under rather general assumptions, the phase diagram of a quasi-one-dimensional repulsive Fermi system consists of two ordered phases: the density wave, spin or charge, and the superconductivity. It is demonstrated that the symmetry of the superconducting order parameter is a non-universal property sensitive to microscopic details of the model. Three potentially stable superconducting states are identified: they are triplet $f$-wave, singlet $d_{x^2-y^2}$-wave, and $d_{xy}$-wave. Presence of multiple competing superconducting states implies that for a real material this symmetry is difficult to predict theoretically and hard to probe experimentally, since artifacts of theoretical approximations or variations in experimental conditions could tip the balance between the superconducting phases.