Collective excitations and mode coupling in layered superconductors

H. A. Fertig; S. Das Sarma

doi:10.1103/PhysRevB.44.4480

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Collective excitations and mode coupling in layered superconductors

H. A. Fertig, S. Das Sarma

DOI 10.1103/PhysRevB.44.4480 · Physical Review B

T1

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Abstract

We investigate the collective-mode spectrum for a layered superconductor structure. For wave vectors directed close to the superlattice axis, we find that the plasmon modes remain below the superconducting gap edge. This is in sharp contrast with the situation for isotropic superconductors in three dimensions, for which the Anderson-Higgs mechanism lifts all such modes out of the gap. We also find that, as a mode crosses the gap edge, either by increasing the wave vector or tilting its direction with respect to the superlattice axis, there is a unique mode-coupling effect between pair-breaking excitations and the collective mode. This manifests itself as a line splitting in the dielectric response, which may in principle be used to determine the gap of such a system. We also calculate the effect of interplane tunneling on the collective-mode spectrum. We find that, if the tunneling rate is large enough, the plasmon modes may all be lifted out of the gap. We show that estimates for the plasmon energy based on the effective-mass approximation can grossly overestimate its minimum value.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	125	Pressure not reported	unknown