Last year, a group of Japanese physicists grabbed headlines around the world by announcing that they could induce superconductivity in a sample of iron telluride by soaking it in red wine. They found that other alcoholic drinks also worked–white wine, beer, sake and so on–but red wine was by far the best.
The question, of course, is why. What is it about red wine that does the trick?
Today, these guys provide an answer, at least in part. Keita Deguchi at the National Institute for Materials Science in Tsukuba, Japan, and a few buddies, say the mystery ingredient is tartaric acid and has the experimental data to show that it plays an important role in the process.
First, some background. Iron-based superconductors were discovered in 2008 and have since become the focus of intense interest. Deguchi and co study iron telluride which does not superconduct unless some of the telluride atoms are replaced with sulphur, forming FeTeS.
But even then, FeTeS doesn’t superconduct unless it goes through a final processing stage; heating it in water, for example.
Nobody knows what this process does or how it can convert an ordinary material into a superconductor. But some liquids are better than others, as determined by the fraction of the sample they convert into a superconductor.
This is the stage Deguchi and co has been puzzling over. Their approach is to make a sample of FeTeS, cut it up into slices and then heat each slice in a different liquid.
Water works quite well but whiskey, shochu and beer are all better. And of course, red wine is the best of all.
Now Deguchi and co have repeated the experiment with different types of red wine to see which works best. They’ve used wines made with a single grape variety including gamay, pinot noir, merlot, carbernet sauvignon and sangiovese.
It turns out that the best performer is a wine made from the gamay grape–for the connoisseurs, that’s a 2009 Beajoulais from the Paul Beaudet winery in central France.
They then analysed the wines to see which ingredient correlated best with superconducting performance and settled on tartaric acid as the likely culprit. The Beaujolais has the highest tartaric acid concentration .
Finally, they repeated the experiment using a mixture of water and tartaric acid to find out how well it performed.
Interestingly, they found that the solution performed better than water alone but not as well as the Beaujolais.
So while tartaric acid is clearly part of the answer, there must be another component of red wine that somehow encourages the transition to a superconducting state.