Tunneling spectra of unconventional quasi-two-dimensional superconductors

Year: 2024

Authors: Pisani L., Moshe AG., Pieri P., Calvanese Strinati G., Deutscher G.

Autors Affiliation: Univ Bologna, Dipartimento Fis & Astron, I-40127 Bologna, Italy; INFN, Sez Bologna, I-40127 Bologna, Italy; NICPB, EE-12618 Tallinn, Estonia; Tel Aviv Univ, Raymond & Beverly Sackler Sch Phys & Astron, IL-6997801 Tel Aviv, Israel; Univ Camerino, Sch Sci & Technol, Phys Div, I-62032 Camerino, Italy; CNR INO, Ist Nazl Ott, Sede Firenze, I-50125 Florence, Italy.

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-T-c 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 T-c. 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.

Journal/Review: PHYSICAL REVIEW B

Volume: 110 (10)      Pages from: L100506-1  to: L100506-6

More Information: Acknowledgement. A.G.M. acknowledges support by the Estonian Research Council under Grant No. MOBJD1103.
KeyWords: Bcs Superconductivity; Bose-condensation; Fluctuation Conductivity; Dimensional Crossover; Magnetic-properties; Evolution; Spectroscopy; Excitations; Dependence; Coherence
DOI: 10.1103/PhysRevB.110.L100506