Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 9: Supraleitung: Eigenschaften, elektronische Struktur, Ordnungsparameter

TT 9.9: Vortrag

Dienstag, 9. März 2004, 12:00–12:15, H20

Strong electron–phonon coupling in the superconducting perovskite MgCNi₃ — •Andreas Wälte¹, G. Fuchs¹, K.-H. Müller¹, A. Handstein¹, K. Nenkov¹, V.N. Narozhnyi¹, H. Rosner², S.-L. Drechsler¹, S.V. Shulga¹, and L. Schultz¹ — ¹Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtzstr. 20, D-01171 Dresden — ²MPI CPFS Dresden, Nöthnitzer Str. 40, D-01187 Dresden

The superconducting state of MgC_xNi₃, a recently discovered perovskite superconductor [1], was characterized by measurements of the specific heat in a temperature range between 2 and 300 K and the resistivity. Analyzing the upper critical field H_c2(0)=11 T and the London penetration depth in terms of impurity scattering rates, evidence for strong electron–phonon coupling was found. From the characteristic phonon frequency ω_ln≈140 K derived from the specific heat data, a superconducting transition temperature of T_c≈15 K is expected. The reduced experimental value of T_c≈7 K implies considerable pair breaking contribution, which is ascribed to ferromagnetic spin fluctuations. Our results are discussed in comparison with related borocarbide superconductors.

[1] T. He et al. Superconductivity in the non-oxide perovskite MgCNi₃. Nature, Vol. 411, May 2001.