Quantum Criticality in the Ferromagnetic Superconductor UCoGe under Pressure and Magnetic Field

Abstract

The pressure-temperature phase diagram of the orthorhombic ferromagnetic superconductor UCoGe was determined by resistivity measurements up to $10.5$GPa. The Curie temperature $T_C$ is suppressed with pressure and vanishes at the critical pressure $p_c\approx 1$GPa. Superconductivity is observed in both the ferromagnetic state at low pressure, and in the paramagnetic state above $p_c$ up to about 4 GPa. Non-Fermi liquid behavior appears in a large pressure range. The resistivity varies linearly with temperature around $p_c$ and evolves continuously with pressure to a $T^2$ Fermi-liquid behavior for $p⪆5$~GPa. The residual resistivity as a function of pressure shows a maximum far above $p_c$ at $p^{\star }=7.2$GPa and the amplitude of the inelastic scattering term of the resistivity decreases by more than one order in magnitude at $p^{\star }$, which appears to mark the entrance into a weakly correlated regime. The pressure dependence of the upper critical field for magnetic field applied along the $b$ and $c$ axis illustrates the drastic difference in the field dependence of the ferromagnetic superconducting pairing. While for $H\parallel b$ axis $H_{c2}(T)$ is driven by the suppression of the ferromagnetic order, it is dominated by the strong initial suppression of the ferromagnetic fluctuations for a field applied in the easy magnetization axis $c$.

6 pages, 4 figures, accepted for publication in Phys. Rev. B

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Cited by in corpus (9)

• Review of U-based Ferromagnetic Superconductors: Comparison between UGe2, URhGe, and UCoGe
• Superconductivity in high-$T_c$ and related strongly correlated systems from variational perspective: Beyond mean field theory
• Phase diagram of UCoGe
• Spin-triplet superconductivity in the paramagnetic UCoGe under pressure studied by ${}^{59}$Co NMR
• Enhancement of superconductivity by pressure-induced critical ferromagnetic fluctuations in UCoGe
• Effect of Pressure on Magnetism of UIrGe
• Pairing interaction in superconducting UCoGe tunable by magnetic field
• Superconductivity at the Pressure-Induced Ferromagnetic Critical Region in UCoGe
• Localization of 5f-electrons and pressure effects on magnetism in U intermetallics in the light of spin-fluctuation theory