title: Raman-scattering measurements and theory of the energy-momentum spectrum for underdoped Bi2Sr2CaCuO(8+δ) superconductors: evidence of an s-wave structure for the pseudogap.
abstract: We reveal the full energy-momentum structure of the pseudogap of underdoped high-Tc cuprate superconductors. Our combined theoretical and experimental analysis explains the spectral-weight suppression observed in the B2g Raman response at finite energies in terms of a pseudogap appearing in the single-electron excitation spectra above the Fermi level in the nodal direction of momentum space. This result suggests an s-wave pseudogap (which never closes in the energy-momentum space), distinct from the d-wave superconducting gap. Recent tunneling and photoemission experiments on underdoped cuprates also find a natural explanation within the s-wave pseudogap scenario.
authors.affiliation: Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau, France and Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sakai
authors.affiliation: Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: S
authors.initials: S
authors.lastname: Blanc
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Civelli
authors.affiliation: Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Gallais
authors.affiliation: Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: M
authors.initials: M
authors.lastname: Cazayous
authors.affiliation: Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: M-A
authors.initials: MA
authors.lastname: Méasson
authors.affiliation: Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Wen
authors.affiliation: Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Xu
authors.affiliation: Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Gu
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany and Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Sangiovanni
authors.affiliation: Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Motome
authors.affiliation: Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Held
authors.affiliation: Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: A
authors.initials: A
authors.lastname: Sacuto
authors.affiliation: Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau, France and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan and Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France and DPMC, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Genève, Suisse.
authors.forename: A
authors.initials: A
authors.lastname: Georges
authors.affiliation: Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Imada