Manifestation of geometric effects in temperature behavior of AC magnetic response of Josephson Junction Arrays
S. Sergeenkov+*, F. M. Araujo-Moreira+
+Departamento de Física e Engenharia Física, Grupo de Materiais e Dispositivos,
Centro Multidisciplinar para o Desenvolvimento de Materiais Cerâmicos,
Universidade Federal de S ao Carlos, SP, 13565-905 S ao Carlos, Brazil
*Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research
141980 Dubna, Moscow Reg., Russia
PACS: 74.25.Ha, 74.50.+r, 74.80.Bj
Abstract
By improving resolution of home-made mutual-inductance
measurements technique, a pronounced step-like structure (with the
number of steps n=4 for all AC fields) has been observed in the
temperature dependence of AC susceptibility in artificially
prepared two-dimensional Josephson Junction Arrays (2D-JJA) of
unshunted Nb-AlOx-Nb junctions with β L(4.2 K) = 30. Using
a single-plaquette approximation of the overdamped 2D-JJA model,
we were able to successfully fit our data assuming that steps are
related to the geometric properties of the plaquette. The number
of steps n corresponds to the number of flux quanta that can be
screened by the maximum critical current of the junctions. The
steps are predicted to manifest themselves in arrays with the
inductance related parameter β L(T) matching a
"quantization" condition β L(0)=2π (n+1).