Theory of Interplay of Nuclear Magnetism and Superconductivity in AuIn2

TL;DR

This paper presents a theoretical study of the coexistence of nuclear magnetism and superconductivity in AuIn2, highlighting the dominant hyperfine interaction and its effects on magnetic order and quasiparticle spectrum.

Contribution

It introduces a model explaining the magnetic order in AuIn2 due to hyperfine interactions and predicts observable effects on the superconducting quasiparticle spectrum.

Findings

Superconducting electrons and nuclear moments interact via hyperfine contact interaction.

Magnetic order forms a spiral or domain-like structure in the superconducting phase.

Oscillatory magnetic order causes a line of nodes in the quasiparticle spectrum.

Abstract

The recently reported coexistence of a magnetic order, with the critical temperature T_M=35 \mu*K, and superconductivity, with the critical temperature T_S=207 m*K, in AuIn_2 is studied theoretically. It is shown that superconducting (S) electrons and localized nuclear magnetic moments (LM's) interact dominantly via the contact hyperfine (EX) interaction, giving rise to a spiral (or domain-like) magnetic order in superconducting phase. The electromagnetic interaction between LM's and S electrons is small compared to the EX one giving minor contribution to the formation of the oscillatory magnetic order. In clean samples (l>\xi_0) of AuIn$_2$ the oscillatory magnetic order should produce a line of nodes in the quasiparticle spectrum of S electrons giving rise to the power law behavior. The critical field H_c(T=0) in the coexistence phase is reduced by factor two with respect to its bare value.