Superconductivity in the heavy-fermion metal UTe2 survives the application of
very high magnetic fields, presenting both an intriguing puzzle and an
experimental challenge. The strong, 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 applied along the
b-axis. Our results reveal a highly directional vortex pinning force in the
field-reinforced phase. The critical current is significantly suppressed for
currents along the c direction, whereas the flux-flow voltage is reduced with
slight angular misalignments–hallmarks of vortex lock-in transitions typically
seen in quasi-2D superconductors like cuprates and pnictides. These findings
challenge the assumption 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. A pair-density-wave-like state at high fields
could naturally induce a layered modulation of the superfluid density, forming
planar structures that confine vortices and guide their sliding in the
flux-flow regime.

Cet article explore les excursions dans le temps et leurs implications.

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