How cooper pairs vanish approaching the Mott insulator in Bi2Sr2CaCu2O8

Y. Kohsaka, C. Taylor, Peter Wahl, A. Schmidt, Jhinhwan Lee, K. Fujita, J. W. Alldredge, K. McElroy, Jinho Lee, H. Eisaki, S. Uchida, D. -H. Lee, Seamus Davis

Research output: Contribution to journalArticlepeer-review

315 Citations (Scopus)


The antiferromagnetic ground state of copper oxide Mott insulators is achieved by localizing an electron at each copper atom in real space (r-space). Removing a small fraction of these electrons ( hole doping) transforms this system into a superconducting fluid of delocalized Cooper pairs in momentum space ( k- space). During this transformation, two distinctive classes of electronic excitations appear. At high energies, the mysterious 'pseudogap' excitations are found, whereas, at lower energies, Bogoliubov quasi- particles - the excitations resulting from the breaking of Cooper pairs should exist. To explore this transformation, and to identify the two excitation types, we have imaged the electronic structure of Bi2Sr2CaCu2O8+delta in r- space and k- space simultaneously. We find that although the low- energy excitations are indeed Bogoliubov quasi- particles, they occupy only a restricted region of k- space that shrinks rapidly with diminishing hole density. Concomitantly, spectral weight is transferred to higher energy r- space states that lack the characteristics of excitations from delocalized Cooper pairs. Instead, these states break translational and rotational symmetries locally at the atomic scale in an energy- independent way. We demonstrate that these unusual r- space excitations are, in fact, the pseudogap states. Thus, as the Mott insulating state is approached by decreasing the hole density, the delocalized Cooper pairs vanish from k- space, to be replaced by locally translational- and rotational- symmetry- breaking pseudogap states in r- space.

Original languageEnglish
Pages (from-to)1072-1078
Number of pages7
Issue number7208
Publication statusPublished - 28 Aug 2008




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