Double-gap superconducting proximity effect in nanotubes

TL;DR

This paper theoretically investigates the superconducting proximity effect in metallic carbon nanotubes, revealing conditions for double-gap superconductivity influenced by interactions and tunneling symmetry.

Contribution

It introduces a theoretical model showing how double-gap superconductivity can occur in nanotubes due to symmetric tunneling and Coulomb interactions.

Findings

Double-gap superconductivity can arise in nanotubes with symmetric tunneling.

Interactions in nanotubes can stabilize superconductivity in both bands.

Highly asymmetric tunneling also supports double-gap superconductivity.

Abstract

We theoretically explore the possibility of a superconducting proximity effect in single-walled metallic carbon nanotubes due to the presence of a superconducting substrate. An unconventional double-gap situation can arise in the two bands for nanotubes of large radius wherein the tunneling is (almost) symmetric in the two sublattices. In such a case, a proximity effect can take place in the symmetric band below a critical experimentally-accessible Coulomb interaction strength in the nanotube. Furthermore, due to interactions in the nanotube, the appearance of a BCS gap in this band stabilizes superconductivity in the other band at lower temperatures. We also discuss the scenario of highly asymmetric tunneling and show that this case too supports double-gap superconductivity.