Dimensionality of the reinforced superconductivity in UTe<sub>2</sub>.

Zhang, L; Guo, C; Graf, D; Putzke, C; Bordelon, M M; Bauer, E D; Thomas, S M; Ronning, F et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Superconductivity in the heavy-fermion metal UTe<sub>2</sub> 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 UTe<sub>2</sub> and point to enhanced two-dimensionality in the high-field state, consistent with a change in the order parameter.