Magnetic pair breaking in superconducting HoNi2B2C studied on a single crystal by thermal conductivity in magnetic fields

Abstract

The magnetic field dependence of the thermal conductivity κ of a HoNi2B2C single crystal (parallel to [110]; 2<T/K<10 ; μ0H≤0.4 T) is reported. It exhibits a characteristic change in the slope of κ(T) at significantly lower temperatures (or lower fields) than the resistively measured critical temperature Tc(H) (or the upper critical field Hc2(T)), thus pointing to an enhanced fraction of quasiparticles due to strong magnetic pair breaking. This demands a careful interpretation of κ(T,H) data for distinct superconductors. Different scenarios for the occurrence of small energy gaps below and above the magnetic-ordering temperatures are discussed including multiband aspects of the superconductivity. In particular, we suggest an improved multiband approach for the commensurate antiferromagnetic phase: whereas a nearly isotropic band unaffected by the rare-earth magnetism shows a BCS-like gap, a second band is strongly affected by the competition between superconductivity and magnetism leading to a second smaller gap. The latter band with relatively large Fermi velocities dominates the thermal conductivity.

Source-reported materials — not catalogue approval

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