New Superconducting and Magnetic Phases Emerge on the Verge of Antiferromagnetism in CeIn$_3$

TL;DR

This study uncovers new superconducting and magnetic phases in CeIn$_3$ near antiferromagnetism under pressure, revealing phase separation and coexistence phenomena, and suggests magnetic fluctuations may mediate superconductivity.

Contribution

It reports the discovery of pressure-induced phase separation and coexistence of superconductivity with antiferromagnetism in CeIn$_3$, a novel finding in heavy fermion systems.

Findings

Phase separation of AFM and PM without quantum transition

Superconductivity coexists with AFM in a specific pressure range

Magnetic fluctuations may mediate Cooper pairing

Abstract

We report the discovery of new superconducting and novel magnetic phases in CeIn$_3$ on the verge of antiferromagnetism (AFM) under pressure ($P$) through the In-nuclear quadrupole resonance (NQR) measurements. We have found a $P$-induced phase separation of AFM and paramagnetism (PM) without any trace for a quantum phase transition in CeIn$_3$. A new type of superconductivity (SC) was found in $P=2.28-2.5$ GPa to coexist with AFM that is magnetically separated from PM where the heavy fermion SC takes place. We propose that the magnetic excitations such as spin-density fluctuations induced by the first-order magnetic phase transition might mediate attractive interaction to form Cooper pairs.