Contact: Prof. Piero Martinoli

Team spring 2002

Array of SNS Josephson junctions - S=Pb (clear), N=Cu (dark) - with the geometry of periodically repeated Sierpinski gaskets

Superconductor-Insulator Transition of Underdoped Cuprates
The heart of investigations carried out at the University of Neuchâtel are classical and quantum ordering phenomena in low-dimensional superconductors. In this context collective and topological excitations as well as disorder, frustration and localization effects play an essential role.

To gain insight into these complex phenomena, we rely on Josephson junction arrays prepared with modern nanofabrication techniques. When studied with very sensitive SQUID-based methods, these model systems provide a unique testing ground to explore in great detail and with high accuracy theoretical predictions emerging from fundamental concepts of condensed matter physics and statistical mechanics. These investigations prove to be very useful to link the physics of the arrays to that of high-temperature superconductors, in particular to the magnetic and critical properties of thin films, another central topic of our experimental activity.
On the theoretical side we aim at understanding the unexpected features observed in the dynamic response of arrays and thin films in the critical region and, within the framework of microscopic models, the existence of a pseudogap above the superconducting transition. The group has established a long standing collaboration with the DPMC of the University of Geneva and the IBM Research Laboratory.

References:
[1] M. Calame et al., Phys. Rev. Lett. 86 (2001), 630.
[2] P. Curty and H. Beck, Phys. Rev. Lett. 85 (2000), 796.