S.E. Barrett, D.J. Durand, C.H. Pennington, C.P. Slichter, et al., "63Cu Knight shifts in the superconducting state of YBa2Cu3O7-d (Tc=90 K)," Physical Review B, 41:6283-96, 1990.

Sean Barrett, C.P. Slichter, J.P. Rice, D.M. Ginsberg (University of Illinois, Urbana): "The nature of the superconducting state in the high-temperature superconductors is currently the focus of much research in condensed-matter physics. A basic question is whether or not these new materials can be described by some variant of the Bardeen-Cooper-Schrieffer (BCS) theory, which explains conventional superconductivity. We measured the so-called Knight shifts of the copper nuclei in YBa2Cu3O7 using nuclear magnetic resonance (NMR) to help answer this question.

"The Knight shift in a metal is the substantial increase of the resonance frequency of a nucleus, relative to its frequency in an insulator. This shift is due to the additional magnetic field seen by the nuclei as a result of the spin paramagnetism of...

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