Münster 1997 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 1: Mesoskopische Systeme

TT 1.2: Hauptvortrag

Montag, 17. März 1997, 10:00–10:30, F1

Transport experiments in superconductor-normal metal heterostructures — •B. Pannetier¹, H. Courtois¹, Ph. Gandit¹, D. Mailly², A. Volkov³, and P. Charlat¹ — ¹CNRS, CRTBT, BP166 F-38042 Grenoble Cedex 9 — ²CNRS-L2M, 196 Avenue H. Ravera, F-92220, Bagneux — ³Inst. Rad. Eng. and Electr., RAS, 103907 Moscow, Russia

We review our recent transport measurements in a diffusive mesoscopic normal metal (N: copper) in contact with a superconducting electrode (S: aluminum). At high temperatures, the Josephson effect is suppressed but the magnetoresistance of a loop shaped sample exhibits large h/2e periodic oscillations with an amplitude decaying with temperature as 1/T [1]. This is the signature of the long range coherence of the low energy electron pairs induced by the Andreev reflection at the N-S interface. This coherent contribution disappears at very low temperature when the thermal diffusion length LT exceeds the size of the sample. We discuss the origin of this so-called re-entrance effect [2]. The I-V characteristics of the mesoscopic N metal exhibits strong non-linear behaviour with a characteristic energy scale given by the Thouless energy.

[1] H. Courtois et al., Phys. Rev. Lett. 76, 130 (1996)

[2] P. Charlat et al., Phys. Rev. Lett., December 1996