Superconductivity-induced Resonance Raman Scattering in Multi-layer High-Tc Superconductors

Abstract

Resonant Raman scattering below Tc has been discovered in several Bi-, Hg-, Tl-based high-Tc superconductors with three or four CuO2-layers. For Bi2Si2Ca2Cu3O10+d, we found an unexpected crossover of the pair-breaking peak in the A1g-spectrum from a broad bump at hw = 6kBTc for Eexc = 2.54eV to a sharp peak at hw = 8kBTc for Eexc = 2.18eV, together with a strong enhancement of the Ca-phonons. Under resonant conditions, the relative positions of the pair breaking peaks in A1g, B1g, and B2g channels are 2Delta(A1g) = 2Delta(B1g) > 2Delta(B2g). This relation implies that the A1g Raman channel is free from the Coulomb screening effect, just as predicted theoretically for a d-wave multi-layer superconductor but have never been observed experimentally thus far. The observed resonance effect is the evidence that the electronic state in the inner CuO2-planes is different from that of the outer CuO2-planes.

16 pages, 6 figures. submitted to Phys.Rev.B

References in corpus (2)

• Electronic structure of the trilayer cuprate superconductor Bi${}_2$Sr${}_2$Ca${}_2$Cu${}_3$O${}_{10+\delta }$
• Superconductivity-induced changes of the phonon resonances in RBa_2Cu_3O_7 (R=rare earth)

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