Mathematics Colloquia and Seminars

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The basic concept in the theory of superconductivity is the pairing of electrons into so called cooper pairs. (The pairing takes place due to a phonon mediated attractive interaction between electrons). BCS theory starts with an ansatz wavefunction that assumes condensation of all pairs into the same state. This seams to contradict Pauli's exclusion principle which forbids electrons to occupy the same state. One expects a breakdown of condensation at high pair densities. BCS theory however does not provide such a critical density since it doesn't allow an external control of the pair number. The talk will introduce the pairing mechanism and sketch out BCS theory to point out the need for a proper handling of Pauli exclusion.