Suppression of electronic friction on Nb films in the superconducting state

Kisiel, Marcin and Gnecco, Enrico and Gysin, Urs and Marot, Laurent and Rast, Simon and Meyer, Ernst. (2011) Suppression of electronic friction on Nb films in the superconducting state. Nature materials, Vol. 10, H. 2. pp. 119-122.

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Official URL: http://edoc.unibas.ch/dok/A6001655

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Investigations on the origins of friction are still scarce and controversial(1-4). In particular, the contributions of electronic and phononic excitations are poorly known(5-11). A direct way to distinguish between them is to work across the superconducting phase transition(7-12). Here, non-contact friction(13-16) on a Nb film is studied across the critical temperature T(C) using a highly sensitive cantilever oscillating in the pendulum geometry in ultrahigh vacuum. The friction coefficient Gamma is reduced by a factor of three when the sample enters the superconducting state. The temperature decay of Gamma is found to be in good agreement with the Bardeen-Cooper-Schrieffer theory(12,17-19), meaning that friction has an electronic nature in the metallic state, whereas phononic friction dominates in the superconducting state. This is supported by the dependence of friction on the probe-sample distance d and on the bias voltage V. Gamma is found to be proportional to d(-1) and V(2) in the metallic state, whereas Gamma similar to d(-4) and Gamma similar to V(4) in the superconducting state. Therefore, phononic friction becomes the main dissipation channel below the critical temperature(16).
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Nanomechanik (Meyer)
UniBasel Contributors:Meyer, Ernst and Marot, Laurent
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Nature Publishing Group
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:11 Oct 2012 15:31
Deposited On:11 Oct 2012 15:21

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