Knight Shift in Metals

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(4) Superconducting state below T C All electrons condense into a single state described by a macroscopic wave function. i r r r e 0 Fermi Dirac statistics does not apply! electrons form pairs that are described by Bose statistics Cooper-pairs, mediated by electron-phonon interaction Concerning the spin there are two possibilities: S 0 in most cases S 1 spin-part odd even orbital part of wavefunction s- d- wave L 0,2,... even with respect to inversion p- f- wave L 1,3,... odd in most superconductors, especially the classical ones: SC pauli 0 at T 0 SC 2 density of the SC condensate T K T independent in the normal state D E F T c T K 0 for T 0 pairs
(5) We can also learn about the symmetry of the orbital part of the wave function, s-wave or d-wave: – s wave + + + + + + – d wave Consider energy gap at the Fermi-surface: energy required to break up Cooper pairs and create unpaired electrons s-wave k y finite gap over entire Fermi surface k x d-wave – nodes where the gap vanishes electrons can be excited even at very small energy + + –
Page 1 and 2: (1) Nuclear Magnetic Resonance (NMR
Page 3: (3) volume in 3 2 4 3 8 B d r co
Page 7 and 8: (7) 1 Spin lattice relaxation rate
Page 9 and 10: (9) 1 T 1 W W 2W 2 4 8 2 e0 e

Knight Shift in Metals

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