Superconductor-to-Spin-Density-Wave Transition in Quasi-One-Dimensional Metals with Ising Anisotropy

TL;DR

This paper investigates the phase transitions between superconductivity and spin-density wave states in quasi-one-dimensional Ising-anisotropic metals, revealing complex phase behavior including first and second order transitions.

Contribution

It introduces a theoretical framework for understanding how Ising anisotropy influences phase competition in coupled chains, identifying conditions for different transition types.

Findings

Spin gap opens due to Ising anisotropy in isolated chains

First order transition separates SDW and triplet superconductivity phases

Second order transition with SO(4) symmetry occurs at specific parameters

Abstract

We study a mechanism for superconductivity in quasi-one-dimensional materials with Ising anisotropy. In an isolated chain Ising anisotropy opens a spin gap; if inter-chain coupling is sufficiently weak, single particle hopping is suppressed and the physics of coupled chains is controlled by a competition between pair hopping and exchange interaction. Spin density wave and triplet superconductivity phases are found separated by a first order phase transition. For particular parameter values a second order transition described by SO(4) symmetry is found.