Superconductivity without attraction in a quasi-one-dimensional metal

TL;DR

This paper demonstrates that quasi-one-dimensional metals can exhibit superconductivity without attractive interactions, driven by many-body effects, with a phase diagram featuring competing density wave and unconventional superconducting phases.

Contribution

It introduces a variational wave function capturing 1D correlations, revealing superconductivity without attraction and mapping the phase diagram with competing phases.

Findings

Superconductivity occurs without attractive interactions.

Phase diagram includes density wave and unconventional superconductivity.

Superconducting order parameter symmetry varies with Hamiltonian details.

Abstract

An array of one-dimensional conductors coupled by transverse hopping and interaction is studied with the help of a variational wave function. This wave function is devised as to account for one-dimensional correlation effects. We show that under broad conditions our system possesses the superconducting ground state even if no attraction is present. The superconducting mechanism is of many-body nature and deviates substantially from BCS. The phase diagram of the model is mapped. It consists of two ordered phases competing against each other: density wave, spin or charge, and unconventional superconductivity. These phases are separated by the first order transition. The symmetry of the superconducting order parameter is a non-universal property. It depends on particulars of the Hamiltonian. Within the framework of our model possible choices are the triplet $f$-wave and the singlet $d_{xy}$-wave. Organic quasi-one-dimensional superconductors have similar phase diagram.