I was delighted to see that Jukka Pekola is going to be at UQ on friday to give the physics colloquium. He is a very gifted experimentalist. i.e., he can do many experiments that other people can't get to work.
I first met Jukka (hard to believe!) 20 years ago. I had just completed a Ph.D with the onerous title, "Nonlinear interaction of zero sound with order parameter collective models in superfluid 3He-B."
This explored various acoustic analogues of non-linear optical effects.
I gave a talk on this work at a conference in Florida and later we went to lunch and Jukka said, "we tried to do the experiment you proposed and it did not work." I was delighted that someone had tried! The proposed experiment was to observe two-phonon absorption by the real squashing mode (one of the 18 order parameter collective modes in 3He-B). This required keeping the superfluid at a constant and uniform millikelvin temperature while dumping large amounts of energy into it to produce large amplitude density oscillations. A very difficult experiment....
Jukka's group had tried the experiment at high pressures. I suggested to Jukka that the effect may be more observable at lower pressures because the non-linear coupling would be larger due to the pressure dependence of a relevant Landau Fermi liquid parameter.
Jukka went back to Helsinki and successfully did the experiment! This was exciting for me. We wrote a paper together describing the results. Later we realised this non-linear effect could be used to map out the dispersion relation for the squashing mode (described in this PRL). I was also invited to a conference in Helsinki and I got to see the lab where it all happened! ( see the photos). I gave an overview/summary of all the work in my conference paper.
This was the first of many fruitful collaborations I have now had with experimentalists. Thanks are due to Jukka for getting me started. I look forward to catching up with him on friday.
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