Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 18: Superconductivity - Properties, Electronic Structure, Order Parameter II

TT 18.6: Talk

Monday, March 7, 2005, 11:30–11:45, TU H2053

Multi-band influence on superconductivity in HoNi₂B₂C — •A. Wälte¹, G. Fuchs¹, Yu.G. Naidyuk², K. Nenkov¹, S.-L. Drechsler¹, D. Souptel¹, H. Rosner³, J. Freudenberger¹, K.-H. Müller¹, G. Behr¹, and L. Schultz¹ — ¹Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtzstr. 20, D-01171 Dresden — ²B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin Ave., 61103 Kharkiv, Ukraine — ³MPI CPFS Dresden, Nöthnitzer Str. 40, D-01187 Dresden

Rare-earth nickel borocarbides RNi₂B₂C reveal, depending on the rare-earth R, superconductivity, magnetism or even a mixture of these competing phenomena [1]. The reduction of the superconducting ordering temperature T_c by magnetic pair-breaking fairly follows the Abrikosov-Gorkov model. However, details of the influence of magnetism on the electron system are not yet well understood. From specific heat measurements and point-contact spectroscopy on HoNi₂B₂C the phonon density of states F(ω) and the spectral function α²F(ω) have been extracted. The characteristic phonon frequency ω_ln≈180 K is similar to ω_ln of non-magnetic LuNi₂B₂C. Comparing the specific heat jumps of both compounds, an unexpectedly strong deviation from the Abrikosov-Gorkov expectation for HoNi₂B₂C is found. A possible explanation is the different influence of pair-breaking on different electron bands.

[1] R.J. Cava et al., Nature 367, January 1994.