Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 10: Superconductivity - Properties, Electronic Structure, Order Parameter
TT 10.1: Vortrag
Dienstag, 27. März 2007, 09:30–09:45, H18
Opening of the Superconducting Energy Gap observed with Neutron Spectroscopy — •Frank Weber1,2, Andreas Kreyssig3,4, Lothar Pintschovius1, Winfried Reichardt1, Oliver Stockert5, Rolf Heid1, Dmitry Reznik1, and Klaudia Hradil6 — 1FZ Karlsruhe, IFP, Karlsruhe — 2PI, Uni Karlsruhe (TH), Karlsruhe — 3IFP, TU Dresden, Dresden — 4Ames Laboratory, Ames, USA — 5MPI-cpfs, Dresden — 6IPC, Uni Göttingen, Aussenstelle FRM II, Garching
We present inelastic neutron scattering data on YNi2B2C (Tc = 15 K). We made a systematic study of the already known phonon anomaly in the (100)-direction [1] as well as of a so far unexplored anomaly at the zone boundary in the (110)-direction (M-point). Our data unambiguously show that the superconductivity-induced changes of the spectral function of phonons with a strong electron-phonon coupling can extremely well be understood in the framework of a theory proposed by Allen et al. [2]. The analysis yields the temperature dependent SC energy gap with high accuracy. As a consequence, even deviations from BCS like behavior can be assessed with confidence. Further, we found that the SC gap extracted from the phonon data for q=(0.5,0,0) and q=(0.5,0.5,0), respectively, differs by a factor 1.4. This is a direct proof for the long discussed anisotropy of the SC energy gap in borocarbides.
[1] Kawano et al., PRL. 77, 4628 (1996), [2] Allen et al., PRB 56, 5552 (1997)