Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Nanotribulogy

O 17.5: Vortrag

Montag, 26. März 2012, 17:00–17:15, A 053

Suppression of electronic friction on Nb-films below the critical temperature — •Marcin Kisiel¹, Enrico Gnecco², Urs Gysin¹, Laurent Marot¹, Simon Rast¹, and Ernst Meyer¹ — ¹University of Basel, Klingelbergstr.82 4056 Basel, Switzerland — ²IMDEA Nanoscience, Campus Universitario de Cantoblanco, Facultad de Ciencias Módulo C-IX, 28049 Madrid, Spain

The origins of non-contact friction are investigated by highly sensitive force microscopy in the pendulum geometry. In this mode probe is suspended perpendicularly to the sample and the tip's vibrational motion is parallel to the surface. In the pendulum geometry very soft (k~mN/m) and therefore sensitive cantilevers can be used avoiding snapping into the contact due to high longitudinal stiffness. The friction forces acting on a sharp probe tip oscillating below 3nm distances from 140nm thick Nb surface have been measured. Measurements reveal a reduction of dissipation in the superconducting state compared to the normal state by a factor 3. Therefore, electronic friction is found to be the dominant dissipation mechanism with power losses of 80ueV/cycle at separations of 0-3nm. Measurement across the critical temperature of Nb film shows that the character of transition is smooth reflecting the increasing normal electron population which are giving rise to the electronic induced friction. A good agreement with the BCS theory has been found in the drop of friction coefficient, as predicted by the theory[1].

1. B. N. J. Persson, Solid State Communications 115, 145 (2000)