Reduction of Pauli paramagnetic pair-breaking effect in antiferromagnetic superconductors

TL;DR

This paper investigates a mechanism in antiferromagnetic superconductors that significantly reduces the Pauli paramagnetic pair-breaking effect, potentially explaining large upper critical fields observed in certain heavy fermion materials.

Contribution

It introduces a mechanism that diminishes Pauli pair-breaking in antiferromagnetic superconductors, applicable even with orbital effects, and models its impact on the upper critical field.

Findings

Upper critical field can exceed the Pauli limit by several times.

The mechanism is demonstrated using a 3D model with magnetic subsystems.

Relevance to large critical fields in CePt_3Si discussed.

Abstract

Antiferromagnetic superconductors in a magnetic field are studied. We examine a mechanism which significantly reduces the Pauli paramagnetic pair-breaking effect. The mechanism is realized even in the presence of the orbital pair-breaking effect. We illustrate it using a three-dimensional model with an intercalated magnetic subsystem. The upper critical field is calculated for various parameters. It is shown that the upper critical field can reach several times the pure Pauli paramagnetic limit. The possible relevance to the large upper critical field observed in the heavy fermion antiferromagnetic superconductor CePt_3Si discovered recently is briefly discussed. We try to understand the large upper critical field in the compound CePt_3Si and field-induced superconductivity in the compound CePb_3 within a unified framework.