Inelastic light scattering from collective modes in a layered superconductor with Cooper-pair tunneling

Wen-Chin Wu; A. Griffin

doi:10.1103/PhysRevB.52.7742

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Inelastic light scattering from collective modes in a layered superconductor with Cooper-pair tunneling

Wen-Chin Wu, A. Griffin

DOI 10.1103/PhysRevB.52.7742 · Physical Review B

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Abstract

In a superconducting bilayer with Cooper-pair tunneling (TJ≠0) between the layers, it has been recently predicted that there should exist in-phase and out-of-phase phase and amplitude fluctuations of the order parameters of the two layers. As a way of observing these phase modes, we calculate the inelastic light scattering from a semi-infinite superconducting superlattice with a bilayer basis. For simplicity, we ignore surface modes. We show that the bulk phase-modes show up as resonances in the isotropic Raman light scattering intensity at finite momentum transfer parallel to the surface. Our specific calculations are for s-wave superconductors but similar results are expected for d-wave pairing. The size of the energy gap of the out-of-phase modes is strongly dependent on the ratio of TJ and the intralayer pairing interaction g, as well as particle-hole damping.