Andreev Spectroscopy of Josephson Coupling

TL;DR

This paper demonstrates that two-electron tunneling spectroscopy via Andreev reflection can effectively probe the energy spectrum and coherent tunneling properties of mesoscopic Josephson junctions, revealing ground and excited state features.

Contribution

It introduces a novel spectroscopic method using Andreev reflection in NSS transistors to analyze Josephson coupling in mesoscopic superconductors.

Findings

Resonant conductance structures reflect ground state properties.

Thresholds in nonlinear I-V curves indicate low-energy excited states.

Method provides detailed insight into Josephson energy spectrum.

Abstract

It is shown that the low energy spectrum of mesoscopic superconductors coupled by Josephson interaction can be probed by two-electron tunneling from a normal electrode. The Andreev reflection in the NS junction of a normal-superconductor-superconductor double junction (NSS transistor) provides a unique spectroscopic tool to probe the coherent Cooper pair tunneling and the energy spectrum of the Josephson (SS) junction. The ground state properties are reflected in a resonant structure of the linear conductance; excited states with an energy as low as the Josephson coupling energy lead to a threshold in the nonlinear $I$-$V$ characteristic.