Magnetic screening in proximity effect Josephson-junction arrays

¹  The Blackett Laboratory, Imperial College - London SW7 2BZ, UK, EU
²  Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering IMT, Photovoltaics and thin film electronics laboratory - Neuchâtel, Switzerland

Received: 2 July 2008
Accepted: 2 March 2009

Abstract

The modulation with magnetic field of the sheet inductance measured on proximity effect Josephson-junction arrays (JJAs) is progressively vanishing on lowering the temperature, leading to a low-temperature field-independent response. This behaviour is consistent with the decrease of the two-dimensional penetration length below the lattice parameter. Low-temperature data are quantitatively compared with theoretical predictions based on the XY model in the absence of thermal fluctuations. The results show that the description of a JJA within the XY model is incomplete and the system is put well beyond the weak screening limit which is usually assumed in order to invoke the well-known frustrated XY model describing classical Josephson-junction arrays.