In all textbooks, the microscopic mechanism of superconductivity is described as an attractive interaction between pairs of electrons which are bound together by lattice polarization forces. The recent discovery of materials which superconduct at unexpectedly high temperatures, raised some doubts on the general validity of this picture. Our prospect was to study their electrodynamic excitation spectrum in the microwave frequency range (0.1 to 10~\cm), where the photon energy is of the same scale as the attractive interaction responsible for the pairing mechanism. In particular we were interested by coherence effect, a characteristic peak that appears in the temperature dependence of the optical conductivity and is a consequence of the peculiar pairing symmetry. By developing a novel detection scheme, we have measured for the first time the conductivity coherence peak on conventional superconductors: Nb and Pb. Then, we have broaden our study to new classes of two-dimensional compounds including organic metals and the cuprates. For all those materials, the inferred pair symmetry was found to be invariant under time reversal, in full agreement with that proposed in the original model.\
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00357898 |
| Date | 01 May 1993 |
| Creators | Klein, Olivier |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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