# Dimensionality of the reinforced superconductivity in UTe2

## TL;DR

The paper investigates the superconducting properties of UTe2 under high magnetic fields, revealing a transition to a two-dimensional superconducting state.

## Contribution

The study identifies a vortex lock-in state in UTe2's high-field superconducting phase, indicating a change in the order parameter.

## Key findings

- Highly directional vortex pinning is observed in the field-reinforced phase of UTe2.
- The critical current is suppressed along the c-direction, suggesting a vortex lock-in transition.
- The results indicate enhanced two-dimensionality in UTe2's high-field superconducting state.

## Abstract

Superconductivity in the heavy-fermion metal UTe2 survives under high magnetic fields, presenting both an intriguing puzzle and an experimental challenge. The non-perturbative influence of the magnetic field complicates the determination of superconducting order parameters in the high-field phases. Here, we report electronic transport anisotropy measurements in precisely aligned microbars in magnetic fields to 45 T. Our results reveal a highly directional vortex pinning force in the field-reinforced phase. The critical current is significantly suppressed for currents only along the c-direction, where the flux-flow voltage vanishes with slight angular misalignments—hallmarks of vortex lock-in transitions typically seen in quasi-2D superconductors like cuprates and pnictides. This marks the observation of a transition into a vortex lock-in state at the boundary between two distinct superconducting states. These findings challenge assumptions of nearly isotropic charge transport in UTe2 and point to enhanced two-dimensionality in the high-field state, consistent with a change in the order parameter.

The authors study microstructured UTe2 by high-field transport, focusing on the field-reinforced superconducting phase. They reveal a highly-directional vortex pinning force typical of quasi-2D superconductors, indicating a vortex lock-in state and consistent with a change of order parameter from the low-field superconducting phase.