Polarization and temperature dependent electronic raman scattering of superconducting Bi 2Sr 2CaCu 2O 8+δ single crystals

Abstract

We report on polarized Raman spectra on the ab-plane of Bi 2Sr 2CaCu 2O 8+δ single crystals in the temperature range from 5 K up to room temperature. The flat continuum of electronic excitations in the normal state of the Bi-2212 compound is redistributed below T c. In A g-symmetry, a superconducting gap is detected with an energy of 2 Δ( T = 5 K) ≈ 336 cm -1 (=42 meV) and its temperature dependence is measured up to T/ T c=0.95. At this temperature, the gap energy is lowered by only 305 with respect to the value at 5 K and thus differs strongly from the BCS behavior. In B 1g-symmetry, the electronic Raman scattering intensity increases nearly linearly from frequencies up to v ̃ ≈480 cm -1 , dropping off at higher frequencies. The lines shapes of our spectra can be described by either intraband (A g-symmetry) or interband electronic Raman scattering (B 1g-symmetry).