Self-reconstruction of order parameter in spin-triplet superconductor UTe$_2$

TL;DR

This study reveals a field-induced phase transition within the superconducting state of UTe$_2$, driven by metamagnetism, which leads to a self-reconstruction of the order parameter and enhances the upper critical field.

Contribution

It demonstrates the self-reconstruction of the order parameter in UTe$_2$ due to metamagnetic crossover, a novel insight into its superconducting state under high magnetic fields.

Findings

Identification of a field-induced phase transition at 5.6 T

Increase of the upper critical field to 12 T

Entropy jump indicating order parameter reconstruction

Abstract

We investigate the effect of easy-axis metamagnetic crossover on superconductivity in UTe$_2$ along the $a$-axis through measurements of AC susceptibility, magnetization, and the magnetocaloric effect. In ultra-clean single crystals, we identify a field-induced phase transition within the superconducting state at 5.6 T, driven by metamagnetism. This transition leads to a high-field superconducting state, significantly increasing the upper critical field to 12 T. A sudden increase in entropy at the transition suggests a self-reconstruction of the order parameter, enabling multi-component superconducting states to adapt to external perturbations.