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