Superconducting Gap Excitations in Bi-Sr-Ca-Cu-O Superconductor Observed by Raman Scattering

Abstract

Raman scattering is measured in the a b plane of the Bi 2.2 Sr 1.8 CaCu 2 O y superconductor. It is found that the electronic Raman scattering appears as a continuum spectrum in both polarized and depolarized scattering and the electronic continuum interferes with some phonon lines. Below T c , the electronic continuum redistributes due to a gap formation and a broad peak appears at about 400 cm -1 , which is larger than the expected value 2 Δ =209 cm -1 of the BCS-theory.