Anisotropic Enhancement of Lower Critical Field in Ultraclean Crystals of Spin-Triplet Superconductor UTe2

Abstract

The paramagnetic spin-triplet superconductor UTe${}_2$ has attracted significant attention because of its exotic superconducting properties including an extremely high upper critical field and possible chiral superconducting states. Recently, ultraclean single crystals of UTe${}_2$ have become available, and thus measurements on these crystals are crucial to elucidate the intrinsic superconducting properties. Here, we report the thermodynamic critical field $H_{\mathrm{c}}$, the lower critical field $H_{c1}$, and the upper critical field $H_{c2}$ at low fields of these high-quality single crystals. From the comparison of the anisotropies in $H_{c1}$ and $H_{c2}$, we find that the experimental $H_{c1}$ values with the magnetic field along $b$- and $c$-axes are anomalously enhanced, showing unusual low-temperature upturns. We propose an effect of the strong Ising-like ferromagnetic fluctuations on the vortex line energy as the origin of the anisotropic enhancement of $H_{c1}$.

7 pages, 6 figures

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Cited by in corpus (7)

• Chiral superconductivity in UTe2 probed by anisotropic low-energy excitations
• A review of UTe${}_2$ at high magnetic fields
• Fully gapped pairing state in spin-triplet superconductor UTe${}_2$
• Enhanced triplet superconductivity in next generation ultraclean UTe2
• Theoretical studies on off-axis phase diagrams and Knight shifts in UTe${}_2$ -- Tetra-critical point, d-vector rotation, and multiple phases
• $b$-axis and $c$-axis Knight shift measurements in the superconducting state on ultraclean UTe${}_2$ with $T_c$ = 2.1 K
• Magnetic edge fields in UTe${}_2$ near zero background fields