Isotope effect on the superfluid density in conventional and high-temperature superconductors

Abstract

We investigate the isotope effect on the London penetration depth of a superconductor which measures nS/m*, the ratio of superfluid density to effective mass. We use a simplified model of electrons weakly coupled to a single phonon frequency ωE, but assume that the energy gap Δ does not have any isotope effect. Nevertheless, we find an isotope effect for nS/m* which is significant if Δ is sufficiently large that it becomes comparable to ωE, a regime of interest to high-Tc cuprate superconductors and possibly other families of unconventional superconductors with relatively high Tc. Our model is too simple to describe the cuprates and it gives the wrong sign of the isotope effect when compared with experiment, but it is a proof of principle that the isotope effect exists for nS/m* in materials where the pairing gap and Tc are not of phonon origin and have no isotope effect.

Source-reported materials — not catalogue approval

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