Mechanism for the Singlet to Triplet Superconductivity Crossover in Quasi-One-Dimensional Organic Conductors

TL;DR

This paper investigates how increasing interchain interactions in quasi-one-dimensional organic conductors induces a transition from singlet to triplet superconductivity, influenced by magnetic fields, using a two-loop renormalization group approach.

Contribution

It demonstrates a mechanism for the singlet to triplet superconductivity crossover driven by interchain interactions and magnetic fields in a quasi-one-dimensional extended Hubbard model.

Findings

Crossover from d-wave to f-wave superconductivity with increasing V_perp

Emergence of triplet superconductivity under magnetic field influence

Vanishing spin gap associated with the crossover

Abstract

Superconductivity of quasi-one-dimensional organic conductors with a quarter-filled band is investigated using the two-loop renormalization group approach to the extended Hubbard model for which both the single electron hopping t_{\perp} and the repulsive interaction V_{\perp} perpendicular to the chains are included. For a four-patches Fermi surface with deviations to perfect nesting, we calculate the response functions for the dominant fluctuations and possible superconducting states. By increasing V_{\perp}, it is shown that a d-wave (singlet) to f-wave (triplet) superconducting state crossover occurs, and is followed by a vanishing spin gap. Furthermore, we study the influence of a magnetic field through the Zeeman coupling, from which a triplet superconducting state is found to emerge.