Field-induced coupled superconductivity and spin density wave order in the Heavy Fermion compound CeCoIn5

TL;DR

This study investigates the high-field superconducting state in CeCoIn5, revealing coupled superconductivity and spin density wave order through muon spin rotation measurements near the upper critical field.

Contribution

It provides experimental evidence for field-induced coupled superconductivity and antiferromagnetic order in CeCoIn5, advancing understanding of heavy fermion superconductors under high magnetic fields.

Findings

Enhanced muon Knight shift at H >= 4.8 T indicating first-order transition.

Detection of paramagnetic spin fluctuations between 2 T and 4.8 T.

Observation of correlated spin fluctuations near Hc2 consistent with theoretical models.

Abstract

The high field superconducting state in CeCoIn5 has been studied by transverse field muon spin rotation measurements with an applied field parallel to the crystallographic c-axis close to the upper critical field Hc2 = 4.97 T. At magnetic fields >= 4.8 T the muon Knight shift is enhanced and the superconducting transition changes from second order towards first order as predicted for Pauli-limited superconductors. The field and temperature dependence of the transverse muon spin relaxation rate sigma reveal paramagnetic spin fluctuations in the field regime from 2 T < H < 4.8 T. In the normal state close to Hc2 correlated spin fluctuations as described by the self consistent renormalization theory are observed. The results support the formation of a mode-coupled superconducting and antiferromagnetically ordered phase in CeCoIn5 for H directed parallel to the c-axis.