New behaviour observed in superconductors

A University of Bath physicist has collaborated in a study which observed behaviour in a superconductor which had never been seen before.

Dr Stephen Clark from the Department of Physics working with experimentalists from the Max Planck Institute for the Structure and Dynamics of Matter observed  “parametric amplification” of terahertz laser light generated by a superconductor.

Between the layers that made up the "cuprate" superconductor are electron pairs that slosh back and forth between each plane – these are known as Josephson plasmons, and they interact strongly with light with terahertz frequencies.

In this experiment, which Dr Clark helped to analyse, a laser was used to directly excite the plasmon inducing large amplitude sloshing. The team found that the highly nonlinear behaviour of Josephson plasmons caused the material to reflect back more radiation than was being shone on it – this is parametric amplification.

Dr Clark said: “This is what happens if you are on a swing and you rock your body at precisely twice the frequency of the swing - you amplify your motion and the swing grows in amplitude. Here we see the same effect inside this material by it emitting additional light, i.e. amplifying, the radiation that was shone on to it. This has never be observed before for Josephson plasmons.”

The study opens up new avenues for “plasmonics”, a field of science utilising plasma waves for transmitting information. These findings are reported in the journal Nature Physics.

More information on the discovery is available on the Max Planck Institute for the Structure and Dynamics of Matter at CFEL website at:

91 per cent of physics research from the University of Bath was judged to be world-leading or internationally excellent by the in the recent independently-assessed Research Excellence Framework 2014.


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