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.
@article{arxiv.cond-mat/9411070,
title = {Andreev Spectroscopy of Josephson Coupling},
author = {F. W. J. Hekking and L. I. Glazman and Gerd Schoen},
journal= {arXiv preprint arXiv:cond-mat/9411070},
year = {2009}
}