Electron transport in single wall carbon nanotube weak links in the Fabry-Perot regime

TL;DR

This paper reports on the fabrication and analysis of superconducting contacts on single-walled carbon nanotubes, revealing Fabry-Perot interference, supercurrent, and subharmonic gap structures, advancing understanding of quantum transport in nanotube weak links.

Contribution

It introduces reproducible high-transparency superconducting contacts on SWCNTs and demonstrates their quantum transport properties in the Fabry-Perot regime.

Findings

Observation of Fabry-Perot interference patterns

Detection of supercurrent and zero-bias conductance peak

Agreement with coherent theory of superconducting point contacts

Abstract

We fabricated reproducible high transparency superconducting contacts consisting of superconducting Ti/Al/Ti trilayers to gated single-walled carbon nanotubes (SWCNTs). The reported semiconducting SWCNT have normal state differential conductance up to $3e^2/h$ and exhibit clear Fabry-Perot interference patterns in the bias spectroscopy plot. We observed subharmonic gap structure in the differential conductance and a distinct peak in the conductance at zero bias which is interpreted as a manifestation of a supercurrent. The gate dependence of this supercurrent as well as the excess current are examined and compared to a coherent theory of superconducting point contacts with good agreement.