from arXiv:1605.04199.  On the left is experiment, in the right is theory.

Theory isn’t always right, and even when it is right, it isn’t always relevant. Sometimes it is hard to tell, in both respects.  Occasionally, though, confirmation of a theory is strikingly clear.  Humans are visual creatures, so we really like to “see” this in a picture.

It’s been about 9 years since my group wrote a paper  of about 4000 words presenting a theory of frustrated antiferromagnets based on the special geometry of the diamond lattice.  We predicted a unique “spiral surface” of strong spin fluctuations in momentum space, which we proposed could be observed by neutron scattering in the material MnSc2S4.  At the time, the experiment was impossible because there were no single crystals available.  A pity.   9 years is a while.  Jason Alicea and Emmanuel Gull, both graduate students at the time, are now successful professors at Caltech and Michigan, respectively, and Simon Trebst, who at the time was a researcher at Microsoft, now is a Professor Doctor in Cologne.   Doron Bergman is making loads of money in the SF Bay area.

But in the last month intrepid experimenters in Europe presented new results, after preparing large enough single crystals to do the measurements.  In this paper, you can actually see the spiral surface – or rather a cut through it, which makes a kind of rounded square, in the raw data.  Pretty cool!