Tuning magnetic confinement of spin-triplet superconductivity

Wen-Chen Lin,Hyunsoo Kim,Sheng Ran,I-Lin Liu,David Graf,Nicholas P. Butch,Daniel J. Campbell,Johnpierre Paglione,Andriy H. Nevidomskyy

doi:10.1038/s41535-020-00270-w

Abstract

Electrical magnetoresistance and tunnel diode oscillator measurements were performed under external magnetic fields up to 41 T applied along the crystallographic b axis (hard axis) of UTe2 as a function of temperature and applied pressures up to 18.8 kbar. In this work, we track the field-induced first-order transition between superconducting and magnetic field-polarized phases as a function of applied pressure, showing suppression of the transition with increasing pressure until the demise of superconductivity near 16 kbar and the appearance of a pressure-induced ferromagnetic-like ground state that is distinct from the field-polarized phase and stable at zero field. Together with evidence for the evolution of a second superconducting phase and its upper critical field with pressure, we examine the confinement of superconductivity by two orthogonal magnetic phases and the implications for understanding the boundaries of triplet superconductivity.

Highlights

Previous work on uranium-based compounds, such as UGe2, URhGe, and UCoGe, has unearthed a rich interplay between superconductivity and ferromagnetism in this family of materials[1], with suggestions that ferromagnetic spin fluctuations can act to enhance pairing[2]
UTe2 has drawn strong attention owing to a fascinating list of properties—including the absence of magnetic order at ambient pressure[3], Kondo correlations, and extremely high upper critical fields4—that have led to proposals of spin-triplet pairing[4,5,6,7], and a chiral order parameter[8,9]
At least two forms of re-entrant superconductivity have been observed in high magnetic fields, including one that extends the low-field superconducting phase upon precise field alignment along the crystallographic b axis[10], and an extreme high-field phase that onsets in pulsed magnetic fields above the paramagnetic normal state at angles tilted away from the b axis[11]

Summary

Introduction

Previous work on uranium-based compounds, such as UGe2, URhGe, and UCoGe, has unearthed a rich interplay between superconductivity and ferromagnetism in this family of materials[1], with suggestions that ferromagnetic spin fluctuations can act to enhance pairing[2]. The magnetic field response of electrical resistance R at low pressures is similar to previous results at ambient pressure, which showed that the superconducting state persists up to the FP phase transition H* of nearly 35 T for H||b, and re-entrant behavior can be observed near Tc for a slight misalignment of the field[10].

Results

Conclusion