Doping dependence of the electron-phonon and electron-spin fluctuation interactions in Bi-2212

ORAL

Abstract

In the BCS theory of conventional superconductors, electrons form (Cooper) pairs via interactions with the underlying crystal lattice. In the cuprate superconductors, it is not clear whether Cooper pairing takes place via electrons interacting with phonons, spin fluctuations, or whether a bosonic mechanism is necessary at all. Though time-integrated optical measurements on the cuprates can give information on the coupling strength between electrons and an effective boson, it is difficult to tell whether one or more bosons are involved, or the nature of these bosons. We report measurements of time-resolved quasiparticle relaxation of Bi$_2 $Sr$_2 $CaCu$_2 $O$_{8+\delta } $ single crystals (hole concentration $p$ = 0.10-0.22). Our data indicate that \textit{two} bosonic modes are associated with superconductivity: the electron-phonon coupling constant ($\lambda _{e-ph} )$ peaks at optimal doping, while the electron-spin fluctuation coupling constant ($\lambda _{e-sf} )$ decreases monotonically with doping.

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Authors

  • Elbert Chia

    Nanyang Technological University

  • Daniel Springer

    Nanyang Technological University

  • Saritha Nair

    Nanyang Technological University

  • Xinaquan Zou

    Nanyang Technological University

  • Siew Ann Cheong

    Nanyang Technological University

  • Christos Panagopoulos

    Nanyang Technological University

  • Antoinette Taylor

    CINT, Los Alamos National Laboratory, Los Alamos National Laboratory

  • Tsuyoshi Tamegai

    Dep. of Appl. Phys., The Univ. of Tokyo, University of Tokyo

  • Hiroshi Eisaki

    Nanoelectronics Research Institute, AIST, Japan, AIST, Japan, AIST, University of Tokyo; CREST, Japan Science and Technology Agency; RIKEN (The Institute of Physical and Chemical Research)

  • Shigeyuki Ishida

    University of Tokyo

  • Shin-ichi Uchida

    Univ. of Tokyo, Tokyo U, University of Tokyo

  • Jian-Xin Zhu

    Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA, Los Alamos National Lab, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, Theoretical Division, Los Alamos National Laboratory, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, Los Alamos National Laboratory