What is it about?
We demonstrate a Josephson oscillator operating at a frequency of few hundred GHz. The generation is caused by a permanent flipping of half integer magnetic flux quantum (semifluxon) in the middle of the Josephson junction. We have measured its output power and radiation line width.
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Why is it important?
The oscillator demonstrated in this work can deliver substantially more power than the oscillators based on an integer fluxon shuttling back and forth along the junction. It also has a dc-to-ac power conversion efficiency about 10%. It is also more compact than the typical flow-flow oscillators used nowadays, still having comparable radiation line width, which is not sensitive to the fluctuations of the injector current.
Read the Original
This page is a summary of: Radiation power and linewidth of a semifluxon-based Josephson oscillator, Applied Physics Letters, February 2014, American Institute of Physics,
DOI: 10.1063/1.4864320.
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Resources
What is semifluxon?
Original paper about semifluxon whic appears in 0-pi Josephson junctions
The first observation of semifluxons in 0-pi-0-pi-... Josephson junctions
Semifluxons were observed by measuring local magnetic field above YBCO-Nb ramp zigzag Josephson junction.
How to create an artificial phase discontinuity in a long Josephson junction?
The generation by flipping semifluxon was present already in this experiment, but its high frequency properties (power, line width) were not studied.
What happens when artificially created phase discontinuity is not ideal?
Non-ideal phase discontinuity affects Ic(H) and I_c(I_inj) dependences and it is shown how it does.
Manipulations with a molecule of two coupled semifluxons
A "molecule" consisting of two antiferromagnetically arranged semifluxons can be in one of two degenerate ground states: semifluxon+antisemifluxon or antisemifluxon+semifluxon. The controllable switching between these states and read-out of the current state are demonstrated.
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