Field Induced Multiple Superconducting Phases in UTe2 along Hard Magnetic Axis

TL;DR

This study maps the complex superconducting phases of UTe2 under magnetic fields along its hard axis, revealing multiple phases and a new intermediate phase with distinct properties, advancing understanding of unconventional superconductivity.

Contribution

It reports the discovery of multiple superconducting phases and an intermediate phase in UTe2 under high magnetic fields along the hard axis, using high-quality single crystals.

Findings

Identification of low- and high-field superconducting phases with contrasting behaviors.

Observation of a consistent field ($H^{igstar}$) where the high-field phase appears.

Detection of an intermediate superconducting phase with small flux pinning forces.

Abstract

The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields ($H$) along the hard magnetic b-axis using a high-quality single crystal with $T_{\rm c} = 2.1$ K. Simultaneous electrical resistivity and AC magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the $H^{\ast}$ of $\sim$15 T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near $H^{\ast}$, indicating an intermediate SC phase characterized by small flux pinning forces.