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

TL;DR

This paper investigates terahertz wave generation from intrinsic Josephson junctions in cuprate superconductors, highlighting the role of soliton configurations and proposing an array-based approach for enhanced emission.

Contribution

It introduces a novel analysis of soliton dynamics in short junctions and proposes an array configuration to improve terahertz emission power.

Findings

Rectangular soliton configurations enable coherent emission.

Triangular soliton lattices are more stable but less coherent.

Array of stacks can produce emission intensity proportional to the square of the number of stacks.

Abstract

The nano-scale intrinsic Josephson junctions in highly anisotropic cuprate superconductors have potential for generation of terahertz electromagnetic waves. When the thickness of a superconductor sample is much smaller than the wavelength of electromagnetic waves in vacuum, the superconductor renders itself as a cavity. Unlike conventional lasers, the presence of the cavity does not guarantee a coherent emission because of the internal degree of freedom of the superconductivity phase in long junctions. We study the excitation of terahertz wave by solitons in a stack of intrinsic Josephson junctions, especially for relatively short junctions. Coherent emission requires a rectangular configuration of solitons. However such a configuration is unstable against weak fluctuations, contrarily solitons favor a triangular lattice corresponding to an out phase oscillation of electromagnetic waves. To utilize the cavity, we propose to use an array of stacks of short intrinsic Josephson junctions to generate powerful terahertz electromagnetic waves. The cavity synchronizes the plasma oscillation in different stacks and the emission intensity is predicted to be proportional to the number of stacks squared.