Pressure-induced superconductivity beyond magnetic quantum criticality in a Kondo ferromagnet

TL;DR

This study discovers pressure-induced superconductivity in a ferromagnetic Kondo lattice material Ce5CoGe2, occurring beyond the magnetic quantum critical point and suggesting unconventional pairing mechanisms.

Contribution

It reveals a new class of correlated materials where superconductivity emerges beyond ferromagnetic quantum criticality, expanding understanding of unconventional superconductivity.

Findings

Superconductivity appears at pressures beyond the magnetic instability.

Ce5CoGe2 transitions from ferromagnetic to antiferromagnetic under pressure.

Superconductivity is associated with a strange-metal state near the QCP.

Abstract

Quantum phase transitions are an established setting for emergent phenomena driven by strong electronic correlations, including strange metals and unconventional superconductivity. These have been explored extensively in Kondo lattice materials tuned to an antiferromagnetic quantum critical point (QCP), but superconductivity emerging near ferromagnetic quantum criticality is not yet observed, and the conditions under which it occurs in proximity to ferromagnetism are undetermined. Here, we report a new setting for superconductivity in the ferromagnetic Kondo-lattice material Ce5CoGe2, where there is a ferromagnetic ground state at ambient pressure, which evolves to antiferromagnetism under applied pressures. The antiferromagnetic transition is suppressed to a zero-temperature QCP, which is accompanied by strange-metal behavior. Superconductivity does not occur at the QCP, but instead appears at pressures beyond the magnetic instability. These findings suggest that Ce5CoGe2 represents a distinct class of correlated materials exhibiting a unique scenario for the emergence of superconductivity, likely associated with unconventional pairing mechanisms beyond spin-fluctuations.