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arXiv · 2409.16804

Tunneling spectra of unconventional quasi-two-dimensional superconductors

L. Pisani·A. G. Moshe·P. Pieri·G. Calvanese Strinati·G. Deutscher
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Abstract

Superfluid condensation can fundamentally be different from that predicted by the Bardeen-Cooper-Schrieffer (BCS) theory. In a broad class of low-carrier-density superconductors, such as granular aluminum, doped nitrides, and high-Tc cuprates, tunneling experiments reveal strong rather than weak coupling, as well as a conductance that does not return to that of the normal state upon approaching the critical temperature Tc. Here, we show that this behavior is in quantitative agreement with a tunneling theory that takes into account the large pairing-fluctuation effects that occur in the crossover region from weak-coupling BCS to strong-coupling Bose-Einstein condensation, provided the coherence energy scale rather than the single-particle energy gap is used to evaluate the coupling ratio. We also propose that the tendency toward strong coupling is a generic property of quasi-2D low-carrier-density superconductors.

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L. Pisani, A. G. Moshe, P. Pieri, G. Calvanese Strinati, G. Deutscher. 2024-09-25. Tunneling spectra of unconventional quasi-two-dimensional superconductors. https://doi.org/10.1103/physrevb.110.l100506

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