Proximity effects in the superconductor/heavy-fermion bilayer system

A. Otop; G. R. Boogaard; R. W. A. Hendrikx; M. B. S. Hesselberth; C. Ciuhu; A. Lodder; J. Aarts

doi:10.1209/epl/i2003-00138-7

All issues

Volume 64 / No 1 (October 2003)

Europhys. Lett., 64 1 (2003) 91-97

Abstract

Issue		Europhys. Lett. Volume 64, Number 1, October 2003


Page(s)		91 - 97
Section		Condensed matter: electronic structure, electrical, magnetic, and optical properties
DOI		https://doi.org/10.1209/epl/i2003-00138-7
Published online		01 November 2003

Europhys. Lett., 64 (1), pp. 91-97 (2003)

Proximity effects in the superconductor/heavy-fermion bilayer system $\chem{Nb/CeCu_6}$

A. Otop¹^,2, G. R. Boogaard¹, R. W. A. Hendrikx¹, M. B. S. Hesselberth¹, C. Ciuhu³, A. Lodder³ and J. Aarts¹

¹ Kamerlingh Onnes Laboratory, Leiden University P.O. Box 9504, 2300 RA Leiden, the Netherlands
² Institut für Metallphysik und Nukleare Festkörperphysik Technische Universität Braunschweig - Mendelssohnstr. 3 38106 Braunschweig, Germany
³ Faculty of Sciences, Vrije Universiteit - De Boelelaan 1081 NL-1081 HV Amsterdam, the Netherlands

Received: 20 March 2003
Accepted: 31 July 2003

Abstract

We have investigated the proximity effect between a superconductor ( $\chem{Nb}$ ) and a “heavy-fermion” system ( $\chem{CeCu_6}$ ) by measuring critical temperatures $T_{\ab{c}}$ and parallel critical fields $H_{\ab{c}2}^{\parallel}(T)$ of $\chem{Nb}$ films with varying thickness deposited on 75 $\un{nm}$ thick films of $\chem{CeCu_6}$ , and comparing the results with the behavior of similar films deposited on the normal metal $\chem{Cu}$ . For $\chem{Nb}$ on $\chem{CeCu_6}$ , we find a strong decrease of $T_{\ab{c}}$ with decreasing $\chem{Nb}$ thickness and a finite critical thickness of the order of 10 $\un{nm}$ . Also, dimensional crossovers in $H_{\ab{c}2}^{\parallel}(T)$ are completely absent, in strong contrast with $\chem{Nb/Cu}$ . Analysis of the data by a proximity effect model based on the Takahashi-Tachiki theory shows that the data can be explained by taking into account both the high effective mass (or low electronic diffusion constant), and the large density of states at the Fermi energy which characterize the heavy-fermion metal.

PACS: 71.27.+a – Strongly correlated electron systems; heavy fermions / 74.50.+r – Tunneling phenomena; point contacts, weak links, Josephson effects

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