Josephson effect in quasi one-dimensional unconventional superconductors

TL;DR

This paper investigates the Josephson effect in quasi-one-dimensional organic superconductors with various pairing symmetries, revealing how electronic structure and zero-energy states influence the temperature dependence of Josephson currents.

Contribution

It introduces a theoretical model incorporating asymmetric hopping to analyze Josephson effects in organic superconductors with p, d, and f wave symmetries, highlighting the role of Fermi surface shape and zero-energy states.

Findings

Josephson current saturates at low temperatures for d wave symmetry without t'

Low-temperature anomalies occur in p and f wave symmetries due to zero-energy states

Asymmetric hopping t' influences the presence of zero-energy states and anomalies

Abstract

Josephson effect in junctions of quasi one-dimensional triangular lattice superconductors is discussed, where the theoretical model corresponds to organic superconductors (TMTSF)_2PF_6. We assume the quarter-filling electron band and p, d and f wave like pairing symmetries in organic superconductors. To realize the electronic structures in organic superconductors, we introduce the asymmetric hopping integral, (t') among second nearest lattice sites. At t'=0, the Josephson current in the d wave symmetry saturates in low temperatures, whereas those in the p and the f wave symmetries show the low-temperature anomaly due to the zero-energy state at the junction interfaces. The low-temperature anomaly appears even in the d wave symmetry in the presence of t', whereas the anomaly is suppressed in the f wave symmetry. The shape of the Fermi surface is an important factor for the formation of the ZES in the quarter-filling electron systems.