We have studied charge transport in a one-dimensional chain of small Josephson junctions using a single-electron transistor. We observe a crossover from time-correlated tunneling of single electrons to that of Cooper pairs as a function of both magnetic field and current. At relatively high magnetic field, single-electron transport dominates and the tunneling frequency is given by f=I/e, where I is the current through the chain and e is the electron's charge. As the magnetic field is lowered, the frequency gradually shifts to f=I/2e for I>200 fA, indicating Cooper-pair transport. For the parameters of the measured sample, we expect the Cooper-pair transport to be incoherent.
@article{arxiv.0705.2964,
title = {Crossover from time-correlated single-electron tunneling to that of Cooper pairs},
author = {J. Bylander and T. Duty and G. Johansson and P. Delsing},
journal= {arXiv preprint arXiv:0705.2964},
year = {2007}
}
Comments
5 pages, 4 figures; v2: minor changes, clarifications, additions