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TT: Tiefe Temperaturen

TT 20: Postersitzung IV (Mesoskopische Systeme, Supraleitung: Massivmaterialien, Bandleiter, Pinning, Vortexdynamik, Transporteigenschaften, Korngrenzen)

TT 20.9: Poster

Donnerstag, 27. März 2003, 14:30–19:00, P2c, P2d

Current noise in diffusive SNS junctions — •C. Hoffmann, F. Lefloch, and M. Sanquer — CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble, France

We investigated the current noise in diffusive Al/Cu/Al - junctions with a large variety of normal part lengths between 0.4 and 60  µ m down to very low temperatures (100  mK). SNS junctions can be tuned from a regime where the electron gas is thermalized by strong electron-electron-interaction (“interacting regime” at low voltage) to a regime where the electrons reach the gap energy by multiple Andreev reflections without inelastic collisions (“collisionless regime”) simply by changing the applied voltage. As a function of the sample length these two regimes are more or less pronounced. In the short junctions the SN-interfaces are connected coherently, we observe a supercurrent and a large collisionless regime where the noise increases linearly with the voltage. This is in good agreement with recent semiclassical theory [1]. In these junctions we also studied the noise behavior at currents just above the critical current in detail. In the longer junctions the SN-interfaces are connected incoherently. We observe a reentrance of the resistance at low energies and the noise shows a very pronounced interacting regime. This allows us to deduce the inelastic scattering length of electron-phonon and electron-electron-interaction [2].

[1] E.V. Bezuglyi et al., Phys. Rev. B 63, 100501 (2001); K.E. Nagaev, Phys. Rev. Lett. 83, 3112 (2001).

[2] C. Hoffmann, F. Lefloch and M. Sanquer, Eur. Phys. J. B 29, 629 (2002).