project title: Experiments on Mesoscopic Squid-Arrays
project leader: Dr. Wiebke Guichard
access given (in days): 92
access used (in days): 65
local host: Prof. Jukka Pekola
home institution: Université Joseph Fourier, Grenoble, France
country of institution: France
starting date (yyyy-mm-dd): 2005-07-01
The goal of the project is to learn about high frequency properties of Josephson junction and SQUID arrays and to make use of them in experiments on Cooper pair pumps and as switches.
Experiments on Cooper pair pumps with SQUID arrays have proven to be difficult due to the arbitrary background charges affecting the small islands between the SQUIDs. No publishable scientific results have been obtained as yet of this effort. Yet, an experiment where SQUIDs are used as switches of photonic heat transport between tiny normal metal islands have worked out beautifully, and we have observed experimentally, as the first group, this heat transport mechanism. We have developed a simple model which explains the observations quantitatively. This effect would be unobservably small, if we would not be able to “chop” the radiative power by applying flux through the SQUIDs. The first set of experiments has been finished [Matthias Meschke, Wiebke Guichard, and Jukka P. Pekola, Single-mode heat conduction by photons, Nature (London) 444, 187 (2006)][21]. In this first set of experiments the full conductance quantum could not be reached because of the low critical current of the SQUID-switches and because of imperfect design of the matching circuit. During the first months of 2007 we have started to design new samples, where the full thermal conductance quantum can possibly be measured accurately. Dr. Guichard will visit LTL for the full month of August 2007 for fabrication of the new samples and for the measurements.