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Nature Physics 2 (2006) 683-686
Observation of the Nernst signal generated by fluctuating Cooper pairs
A. Pourret1, H. Aubin1, J. Lesueur1, C.A. Marrache-Kikuchi2, L. Berge2, L. Dumoulin2, K. Behnia1

Long-range order is destroyed in a superconductor warmed above its critical temperature (Tc). However, amplitude fluctuations of the superconducting order parameter survive and lead to a number of well established phenomena such as paraconductivity : an excess of charge conductivity due to the presence of short-lived Cooper pairs in the normal state. According to an untested theory, these pairs generate a transverse thermoelectric (Nernst) signal. In amorphous superconducting films, the lifetime of Cooper pairs exceeds the elastic lifetime of quasi-particles in a wide temperature range above Tc; consequently, the Cooper pairs Nernst signal dominate the response of the normal electrons well above Tc. In two dimensions, the magnitude of the expected signal depends only on universal constants and the superconducting coherence length, so the theory can be unambiguously tested. Here, we report on the observation of a Nernst signal in such a superconductor traced deep into the normal state. Since the amplitude of this signal is in excellent agreement with the theoretical prediction, the result provides the first unambiguous case for a Nernst effect produced by short-lived Cooper pairs.
1 :  LSLP - Laboratoire de Spectroscopie en Lumière Polarisée
2 :  CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse
Physique/Matière Condensée/Autre

Physique/Matière Condensée/Electrons fortement corrélés

Physique/Matière Condensée/Supraconductivité
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