Radiation of Terahertz Electromagnetic Waves from Build-in Nano Josephson Junctions of Cuprate High-Tc Superconductors

摘要

The nano-scale intrinsic Josephson junctions in highly anisotropic cupratesuperconductors have potential for generation of terahertz electromagneticwaves. When the thickness of a superconductor sample is much smaller than thewavelength of electromagnetic waves in vacuum, the superconductor rendersitself as a cavity. Unlike conventional lasers, the presence of the cavity doesnot guarantee a coherent emission because of the internal degree of freedom ofthe superconductivity phase in long junctions. We study the excitation ofterahertz wave by solitons in a stack of intrinsic Josephson junctions,especially for relatively short junctions. Coherent emission requires arectangular configuration of solitons. However such a configuration is unstableagainst weak fluctuations, contrarily solitons favor a triangular latticecorresponding to an out phase oscillation of electromagnetic waves. To utilizethe cavity, we propose to use an array of stacks of short intrinsic Josephsonjunctions to generate powerful terahertz electromagnetic waves. The cavitysynchronizes the plasma oscillation in different stacks and the emissionintensity is predicted to be proportional to the number of stacks squared.