Point-contact spectroscopy of the antiferromagnetic superconductor HoNi2B2C in the normal and superconducting state

Abstract

Point-contact (PC) spectroscopy measurements on antiferromagnetic (AF) (T_N=5.2K) HoNi2B2C single crystals in the normal and two different superconducting (SC) states (T_c=8.5K and $T_c^{\ast }=5.6K)arereported.ThePCstudyoftheelectron-boson(phonon)interaction(EB(P)I)spectralfunctionrevealspronouncedphononmaximaat16,22and34meV.Forthefirsttimethehighenergymaximaatabout50meVand100meVareresolved.Additionally,anadmixtureofacrystalline-electric-field(CEF)excitationswithamaximumnear10meVanda‘magnetic‘peaknear3meVareobserved.Thecontributionofthe10-meVpeakinPCEPIconstant{\lambda }_{P}Cisevaluatedas20-30$T_c^*=5.6K<T_c, with 2Δ/kT_c^*=3.9. The strong coupling Eliashberg analysis of the low-temperature SC phase with T_c^*=5.6K =T_N, coexisting with the commensurate AF structure, suggests a sizable value of the EPI constant λ_s=0.93. We also provide strong support for the recently proposed by us ''Fermi surface (FS) separation'' scenario for the coexistence of magnetism and superconductivity in magnetic borocarbides, namely, that the superconductivity in the commensurate AF phase survives at a special (nearly isotropic) FS sheet without an admixture of Ho 5d states. Above T_c^* the SC features in the PC characteristics are strongly suppressed pointing to a specific weakened SC state between T_c* and T_c.

arXiv comment11 pages, 8 figs, to be published in PRB, Vol.75, Iss.21

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• Single 20meV boson mode in KFe2As2 detected by point-contact spectroscopy
• Point-contact study of the LuNi2B2C borocarbide superconducting film
• Small-Angle Neutron Scattering and Magnetization Study of HoNi2B2C
• The Superconducting Gap Behavior in the Antiferromagnetic Nickel-Borocarbide Compounds RNi2B2C (R=Dy, Ho, Er, Tm) Studied by Point-Contacts Spectroscopy
• Superconductivity in hole-doped germanium point contacts
• Electron-phonon interaction, magnetic phase transition, charge density waves and resistive switching in VS2 and VSe2 revealed by Yanson point contact spectroscopy