Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.41: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Pecularities of the superconducting gaps and the fermion-boson interaction in TmNi₂B₂C as seen by point-contact spectroscopy — •Oksana Kvitnitskaya^1,2, Yurii Naidyuk¹, Lidiya Tiutrina¹, Igor Yanson¹, Günter Fuchs², Konstantin Nenkov², Günter Behr², and Stefan-Ludwig Drechsler² — ¹ILT Kharkiv, Ukraine — ²IFW Dresden

Point-contact (PC) investigations on the title compound in the normal and superconducting (SC) state (T_c≃ 10.6 K) are presented. The T-dependence of two SC gaps in TmNi₂B₂C determined by Andreev-reflection spectroscopy deviates from the BCS behavior in displaying a maximum at about T_c/2. Additional evidence for the presence of a 2nd gap half as large as the main gap is given. For the first time “reentrant” features were found in the Andreev-reflection spectra measured in magnetic fields. The PC spectroscopy of the fermion-boson interaction in TmNi₂B₂C reveals a pronounced phonon maximum at 9.5 meV and a more smeared one around 15 meV, while at higher energies the PC spectra are almost featureless. Additionally, the intense peak slightly above 3 meV observed in the PC spectra of TmNi₂B₂C, is presumably caused by crystalline-electric-field excitations. The peak near 1 meV detected for some spectra is connected with a modification of the crystal electric field probably due to boron or carbon vacancies.