Comparison of two superconducting phases induced by a magnetic field in UTe2

Superconductivity induced by a magnetic field near metamagnetism is a striking manifestation of magnetically-mediated superconducting pairing. After being observed in itinerant ferromagnets, this phenomenon was recently reported in the orthorhombic paramagnet UTe2. Here we explore the phase diagram of UTe2 under two magnetic-field directions: the hard magnetization axis b, and a direction titled by similar or equal to 25-30 degrees from b in the (b,c) plane. Zero-resistivity measurements confirm that superconductivity is established beyond the metamagnetic field H-m in the tilted-field direction. While superconductivity is locked exactly at fields either smaller (for H||b), or larger (for H tilted by similar or equal to 27 degrees from b to c), than H-m, the variations of the Fermi-liquid coefficient in the electrical resistivity and of the residual resistivity are similar for the two field directions. The resemblance of the normal states for the two field directions puts constraints for theoretical models of superconductivity and implies that some subtle ingredients must be in play. In a magnetic field, superconductivity can be induced or reinforced near a metamagnetic transition, where ferromagnetic fluctuations are suspected to mediate the pairing strength of the Cooper pairs. Here, the authors investigate the superconductor UTe2 and report on the variation in the superconducting properties as the magnetic field is applied along two particular crystallographic axes and their relation to metamagnetism.

Automated summary

Superconductivity induced by a magnetic field near metamagnetism is observed in the orthorhombic paramagnet UTe2. The study investigates the variation in superconducting properties under different magnetic-field directions and their relation to metamagnetism. The similar behavior of superconductivity in different field directions poses constraints on theoretical models and suggests the involvement of subtle factors.