IV-characteristics and power of emission from stacks of long Josephson junctions with Gaussian spread of critical currents

Abstract

The creation of sources of coherent emission in the terahertz region of frequencies from stacks of intrinsic Josephson junctions in high-temperature superconductors becomes the recently important problem of applied nanoscience. We investigated numerically IV-characteristics of stacks of three and four long Josephson junctions and power of emission from edges of the stack at different small Gaussian standard deviations of critical currents. We found the split zero-field steps in IV-characteristics. Positions of zero-field steps in the IV-curve can be described by a simple analytical expression in the theory of electrical properties of stacks of Josephson junctions placed in the external magnetic field. Maxima of coherent emission appear at voltages corresponding to the frequencies of the resonance of the in-phase collective modes of the whole stack with modes of geometrical resonances. We found maximal tolerant standard deviations of critical currents at which this resonance exists (from 1 to 10% of averaged critical currents of junctions).