Physical Review X (Mar 2014)

Strain-Induced Enhancement of the Electron Energy Relaxation in Strongly Correlated Superconductors

  • C. Gadermaier,
  • V. V. Kabanov,
  • A. S. Alexandrov,
  • L. Stojchevska,
  • T. Mertelj,
  • C. Manzoni,
  • G. Cerullo,
  • N. D. Zhigadlo,
  • J. Karpinski,
  • Y. Q. Cai,
  • X. Yao,
  • Y. Toda,
  • M. Oda,
  • S. Sugai,
  • D. Mihailovic

DOI
https://doi.org/10.1103/PhysRevX.4.011056
Journal volume & issue
Vol. 4, no. 1
p. 011056

Abstract

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We use femtosecond optical spectroscopy to systematically measure the primary energy relaxation rate Γ_{1} of photoexcited carriers in cuprate and pnictide superconductors. We find that Γ_{1} increases monotonically with increased negative strain in the crystallographic a axis. Generally, the Bardeen-Shockley deformation potential theorem and, specifically, pressure-induced Raman shifts reported in the literature suggest that increased negative strain enhances electron-phonon coupling, which implies that the observed direct correspondence between a and Γ_{1} is consistent with the canonical assignment of Γ_{1} to the electron-phonon interaction. The well-known nonmonotonic dependence of the superconducting critical temperature T_{c} on the a-axis strain is also reflected in a systematic dependence T_{c} on Γ_{1}, with a distinct maximum at intermediate values (∼16 ps^{−1} at room temperature). The empirical nonmonotonic systematic variation of T_{c} with the strength of the electron-phonon interaction provides us with unique insight into the role of electron-phonon interaction in relation to the mechanism of high-T_{c} superconductivity as a crossover phenomenon.