Europhys. Lett.
Volume 67, Number 1, July 2004
Page(s) 110 - 116
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 June 2004
Europhys. Lett., 67 (1) , pp. 110-116 (2004)
DOI: 10.1209/epl/i2003-10293-9

Current-current correlations in hybrid superconducting and normal-metal multiterminal structures

G. Bignon1, M. Houzet2, F. Pistolesi1 and F. W. J. Hekking1

1  Laboratoire de Physique et Modélisation des Milieux Condensés, CNRS and Université Joseph Fourier - B.P. 166, 38042 Grenoble, France
2  Commissariat à l'Énergie Atomique, DSM/DRFMC/SPSMS F-38054 Grenoble, France

(Received 15 October 2003; accepted in final form 30 April 2004)

We consider a hybrid system consisting of two normal metal leads weakly connected to a superconductor. Current-current correlations of the normal leads are studied in the tunneling limit at subgap voltages and temperatures. We find that only two processes contribute to the cross-correlation: the crossed Andreev reflection (emission of electrons in different leads) and the elastic cotunneling. Both processes are possible due to the finite size of the Cooper pair. Noise measurements can thus be used to probe directly the superconducting wave function without the drawbacks appearing in average current measurements where the current is dominated by direct Andreev reflection processes. By tuning the voltages it is possible to change the sign of the cross-correlation. Quantitative predictions are presented both in the diffusive and ballistic regimes.

74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects.
74.45.+c - Proximity effects; Andreev effect; SN and SNS junctions.
74.40.+k - Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.).

© EDP Sciences 2004