2000/12/31 by K. C. Hewitt, J. C. Irwin
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.66.054516
published as Phys. Rev. B 66, 054516 (2002) · 9 pages REvTex document including 8 eps figures; new table II; changes to Fig. 5 and text
openalex publication_date 2002/08/12 · arxiv created 2002/11/06 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Bi2Sr2CaCu2O_8+\ensuremathδ crystals with varying hole concentrations (0.12<p<0.23) were studied to investigate the effects of doping on the symmetry and magnitude of the superconducting gap [\ensuremathΔ(k)]. Electronic Raman scattering experiments that sample regions of the Fermi surface near the diagonal (B2g) and principal axes (B1g) of the Brillouin zone have been utilized. The frequency dependence of the Raman response function \ensuremathχ^\ensuremath'' at low energies [\ensuremathω<\ensuremathΔ(k)] is found to be linear for B2g and cubic for B1g (T<Tc). The latter observations have led us to conclude that the doping dependence of the superconducting gap is consistent with d_x2\ensuremath-y2 symmetry, for slightly underdoped and overdoped crystals. Studies of the pair-breaking peak found in the B1g spectra demonstrate that the magnitude of the maximum gap (|\ensuremathΔmax|) decreases monotonically with increasing hole doping, for p>0.12. Based on the magnitude of the B1g renormalization, it is found that the number of quasiparticles participating in pairing increases monotonically with increased doping. On the other hand, the B2g spectra show a weak ``pair-breaking peak'' that follows a paraboliclike dependence on hole concentration, for 0.12<p<0.23.