Diffusion current in a system of coupled Josephson junctions
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DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Diffusion Current in a System of Coupled Josephson Junctions Yu. M. Shukrinova,b,c,* and I. R. Rahmonova,c a
Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia b Dubna International University, Dubna, Moscow oblast, 141980 Russia cUmarov Physicotechnical Institute, Academy of Sciences of the Republic of Tajikistan, Dushanbe, 734063 Tajikistan *email: [email protected] Received January 18, 2012
Abstract—The role of a diffusion current in the phase dynamics of a system of coupled Josephson junctions (JJs) has been analyzed. It is shown that, by studying the temporal dependences of the superconducting, quasiparticle, diffusion, and displacement currents and the dependences of average values of these currents on the total current, it is possible to explain the main features of the current–voltage characteristic (CVC) of the system. The effect of a diffusion current on the character of CVC branching in the vicinity of a critical current and in the region of hysteresis, as well as on the part of CVC branch corresponding to a parametric resonance in the system is demonstrated. A clear interpretation of the differences in the character of CVC branching in a model of capacitively coupled JJs (CCJJ model) and a model of capacitive coupling with dif fusion current (CCJJ+DC model) is proposed. It is shown that a decrease in the diffusion current in a JJ leads to the switching of this junction to an oscillating state. The results of model calculations are qualitatively con sistent with the experimental data. DOI: 10.1134/S1063776112070151
1. INTRODUCTION The notion of the intrinsic Josephson effect, according to which Cooper’s pairs tunnel between adjacent superconducting CuO2 planes in strongly anisotropic layered cuprate hightemperature super conductors (HTSs) [1], allows an HTS to be treated as a system of coupled Josephson junctions (JJs). This concept is a constituent part in several theories of the hightemperature superconductivity and is of primary importance for determining the current–voltage char acteristics (CVCs) of HTSbased tunneling structures and studying the properties of vortex lattices in related materials [2–5]. Intrinsic tunneling is interesting not only as an object for investigation, but also as a power ful tool for studying the nature of hightemperature superconductivity, the character of transport in the direction perpendicular to the superconducting layers, and the physics of vortices [6]. A model for describing the physical properties of intrinsic JJs in HTSs, includ ing nonlinear effects and various nonequlibrium phe nomena, is offered by a system of coupled JJs [7, 8]. It should be emphasized that the system of coupled JJs is a promising object in HTS electronics that has been extensively studied in recent years [6, 9–11]. In particular, broad possibilities for various applications are offered by the recently discovered coherent elec tromagnetic radiation of noticeable power in a tera hertz frequency rang
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