Electronic and phononic Raman scattering in detwinned YBa2Cu3O6.95 and Y0.85Ca0.15Ba2Cu3O6.95: s-wave admixture to the dx2y2-wave order parameter

M. Bakr, A. P. Schnyder, L. Klam, D. Manske, C. T. Lin, B. Keimer, M. Cardona, and C. Ulrich
Phys. Rev. B 80, 064505 – Published 10 August 2009

Abstract

Inelastic light (Raman) scattering has been used to study electronic excitations and phonon anomalies in detwinned, slightly overdoped YBa2Cu3O6.95 and moderately overdoped Y0.85Ca0.15Ba2Cu3O6.95 single crystals. In both samples modifications of the electronic pair-breaking peaks when interchanging the a and b axis were observed. The lineshapes of several phonon modes involving plane and apical oxygen vibrations exhibit pronounced anisotropies with respect to the incident and scattered light-field configurations. Based on a theoretical model that takes both electronic and phononic contributions to the Raman spectra into account, we attribute the anisotropy of the superconductivity-induced changes in the phonon lineshapes to a small s-wave admixture to the dx2y2 pair wave function. Our theory allows us to disentangle the electronic Raman signal from the phononic part and to identify corresponding interference terms. We argue that the Raman spectra are consistent with an s-wave admixture with an upper limit of 20%.

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  • Received 19 March 2009

DOI:https://doi.org/10.1103/PhysRevB.80.064505

©2009 American Physical Society

Authors & Affiliations

M. Bakr1, A. P. Schnyder2, L. Klam1, D. Manske1, C. T. Lin1, B. Keimer1, M. Cardona1, and C. Ulrich1

  • 1Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
  • 2Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA

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Vol. 80, Iss. 6 — 1 August 2009

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