Pairing in a dry Fermi sea.
In the traditional Bardeen-Cooper-Schrieffer theory of superconductivity, the amplitude for the propagation of a pair of electrons with momentum k and -k has a log singularity as the temperature decreases. This so-called Cooper instability arises from the presence of an electron Fermi sea. It means that an attractive interaction, no matter how weak, will eventually lead to a pairing instability. However, in the pseudogap regime of the cuprate superconductors, where parts of the Fermi surface are destroyed, this log singularity is suppressed, raising the question of how pairing occurs in the absence of a Fermi sea. Here we report Hubbard model numerical results and the analysis of angular-resolved photoemission experiments on a cuprate superconductor. In contrast to the traditional theory, we find that in the pseudogap regime the pairing instability arises from an increase in the strength of the spin-fluctuation pairing interaction as the temperature decreases rather than the Cooper log instability.
Computer Science and Mathematics Division, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, 1 Bethel Valley Road, PO Box 2008, Oak Ridge, Tennessee 37831-6494, USA.
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Maier
IBM Research-Zürich, CH-8803 Rüschlikon, Switzerland.
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Staar
Joint Institute of Computational Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Mishra
Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714, USA.
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Chatterjee
Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA 22904.
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Campuzano
Department of Physics, University of California, Santa Barbara, California 93106-9530, USA.
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Scalapino