<p>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 <Emphasis Type="BoldItalic">c-</Emphasis>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.</p>

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Dimensionality of the reinforced superconductivity in UTe2

  • L. Zhang,
  • C. Guo,
  • D. Graf,
  • C. Putzke,
  • M. M. Bordelon,
  • E. D. Bauer,
  • S. M. Thomas,
  • F. Ronning,
  • P. F. S. Rosa,
  • P. J. W. Moll

摘要

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.