Triplet superconductivity in coupled odd-gon rings

TL;DR

This paper proposes a new mechanism for spin-triplet superconductivity based on melting of macroscopic spin polarization in systems with coupled odd-gon units, demonstrated in quasi-one-dimensional materials and generalizable to other geometries.

Contribution

It introduces a versatile mechanism for spin-triplet pairing mediated by odd-gon units and derives an effective Hamiltonian applicable to various coupled odd-gon systems.

Findings

Application to A2Cr3As3 superconductors shows triplet pairing

Derived a simple effective Hamiltonian for odd-gon systems

Suggests odd-numbered geometric units as promising for triplet superconductivity

Abstract

Shedding light on the nature of spin-triplet superconductivity has been a long-standing quest of solid-state physics since the discovery of superfluidity in liquid $^3$He. Nevertheless, the mechanism of spin-triplet pairing is much less understood than that of spin-singlet pairing explained by the Bardeen-Cooper-Schrieffer theory or even observed in high-temperature superconductors. Here we propose a versatile mechanism for spin-triplet superconductivity, which is mediated through a melting of macroscopic spin polarization in weakly coupled odd-gon-unit system (e.g., triangular unit, pentagon unit, etc). We demonstrate the application of this mechanism by considering a new class of quasi-one-dimensional superconductors A$_2$Cr$_3$As$_3$ (A=K, Rb, and Cs). Furthermore, we derive a simple effective Hamiltonian to easily illustrate the adaptability of the mechanism to general coupled odd-gon-unit systems. We thus argue that materials consisting of odd-numbered geometric units would be a prospect of spin-triplet superconductivity.