Mechanism for Odd Parity Superconductivity in Iron-Based Superconductors

TL;DR

This paper proposes that iron-based superconductors exhibit an odd parity s-wave spin-singlet pairing state driven by local d-p hybridization, revealing a new quantum state of matter and guiding future experimental verification.

Contribution

It introduces a novel odd parity s-wave pairing mechanism in iron-based superconductors based on a single trilayer model, challenging previous parity assumptions.

Findings

Superconducting state classified as odd parity s-wave spin-singlet

Order parameter combines inter-sublattice pairing and intra-sublattice η-pairing

Measurement of odd parity can reveal high-temperature superconducting mechanisms

Abstract

Under the assumption that superconducting pairing is driven by local d-p hybridization, we show that the superconducting state in iron-based superconductors is classified as an odd parity s-wave spin-singlet pairing state in a single trilayer FeAs/Se, the building block of the materials. In a low energy effective model with only d-orbitals in an iron square bipartite lattice, the superconducting order parameter in this state is a combination of a s-wave normal pairing between two sublattices and a s-wave $\eta$-pairing within the sublattices. Parity conservation was violated in proposed superconducting states in the past. The results demonstrate iron-based superconductors being a new quantum state of matter and suggest that a measurement of odd parity can establish fundamental principles related to high temperature superconducting mechanism.