Direct Observation of the Spillover of High Magnetic Field-induced SC3 Superconductivity Outside the Spin-Polarized State in UTe2

TL;DR

This study provides direct evidence that the SC3 superconducting phase in UTe2 extends beyond the spin-polarized state, observed through zero resistance measurements up to 45 T, supporting the role of quantum critical fluctuations in pairing.

Contribution

The paper extends the magnetic field range of previous studies, conclusively demonstrating the spillover of SC3 superconductivity outside the polarized paramagnetic state in UTe2.

Findings

SC3 phase persists beyond the spin-polarized state

Zero resistance observed below 45 T at low temperatures

Supports quantum critical fluctuations mediating pairing

Abstract

In our recent study of the high magnetic field phase landscape of UTe$_2$ [Phys. Rev. X 15, 021019 (2025)] we found indirect evidence that the SC3 superconducting phase spills out beyond the first-order phase boundary of the spin-polarized state. This prior study was limited to a maximal field strength of 41.5 T, and mapped the $b-ac$ rotation plane. Here we measure a high quality sample with residual resistivity ratio RRR = 605 under rotations in the $b-c$ plane up to 45 T. This extended field range helps to unambiguously demonstrate the spillover of SC3 outside the polarized paramagnetic state. This is identified by the observation of zero resistance at low temperatures, for magnetic field strengths lower than the metamagnetic transition field resolved at higher temperatures. This observation is consistent with the scenario that electronic pairing of the SC3 phase is mediated by quantum critical fluctuations.