Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 29: Superconductivity - Mechanisms, Phase Diagram, Competing Order
TT 29.6: Vortrag
Donnerstag, 29. März 2007, 17:15–17:30, H18
Nernst Effect in NdBa2{Cu1−yNiy}3O7−δ — •Niko Johannsen1, Thomas Wolf2, Thomas Lorenz1, and John Mydosh1 — 1II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — 2Forschungszentrum Karlruhe, IFP, 76021 Karlsruhe
More than 20 years after its discovery the mechanism of high-temperature superconductivity is still unsolved. Possible relations to other anomalous phenomena in High-Tc materials such as the pseudogap may play a key role towards an understanding of this mechanism. The Nernst effect is an excellent probe to detect vortices and vortex-like excitations1. In NdBa2{Cu1−yNiy}3O7−δ, adding magnetic Ni-impurities leads to a suppression of Tc but at the same time the pseudogap is strongly enhanced2. So this is an ideal system to study possible relations between superconductivity and the pseudogap. We present measurements on a series of optimally doped (O7) and underdoped (O6.8) samples with Ni contents ranging from y=0 to 0.12. In all samples an onset of the Nernst signal (Tν) can be found above Tc.
Tν decreases with increasing Ni content as does Tc for the optimally doped samples. The underdoped samples show a slightly different behaviour. The onset of the Nernst signal is not affected when increasing the Ni content from y=0 to 0.03.
Supported by the DFG through SFB 608.
1 Wang et al., PRB 73, 024510 (2006)
2 Pimenov et al., PRL 94, 227003 (2005)