Unconventional superconductivity emerging along with the strange-metal behavior in UAs2 under pressure

TL;DR

This study reports the emergence of superconductivity up to 4 K in UAs2 under high pressure, coinciding with strange-metal behavior and quantum criticality, highlighting unconventional superconductivity in uranium-based materials.

Contribution

It is the first to observe superconductivity in UAs2 under pressure and links it to strange-metal behavior and quantum criticality in a 5f-electron system.

Findings

Superconductivity appears at ~26.8 GPa with Tc = 4 K.

Normal state resistance shows linear temperature dependence indicating strange-metal behavior.

Superconductivity is robust against magnetic fields with Hc2(0) ~ 12 T.

Abstract

The recently discovered spin-triplet superconductor candidate UTe2 with Tc = 2 K has attracted enormous attention because it possesses many interesting properties, such as the extremely high upper critical field Hc2(0), chiral superconductivity and spontaneous time-reversal symmetry breaking, etc., all these suggest that it may be the long-sought spin-triplet superconductor. Here we report the discovery of superconductivity up to Tc = 4K in one of its siblings, i.e., UAs2 under high pressures. Interestingly, the UAs2 shows metallic behavior with an antiferromagnetic (AFM) transition at about 274 K under ambient pressure. Upon applying pressure, this transition is pushed down to lower temperatures with improved electric conductivity. When the pressure rises to about 20-22 GPa, superconductivity occurs together with the emergence of a linear temperature dependence of normal state resistance, the latter is a hallmark of the strange-metal state. The superconductivity with the highest Tc = 4 K is reached under a pressure of about 26.8 GPa, and it is robust against magnetic field with the upper critical field {\mu}0Hc2(0) ~ 12 T, far beyond the Pauli limit. Higher pressures will suppress the superconductivity and bring back the Fermi liquid behavior, showing a clear signature of quantum criticality. Our results open a new avenue for investigating the unconventional superconductivity concerning the mysterious 5f-band electrons in this uranium-based system.