Machine learning illuminates material's hidden order Cornell Chronicle

Extreme temperature can do strange things to metals. In severe heat, iron ceases to be magnetic. In devastating cold, lead becomes a superconductor. For the last 30 years, physicists have been stumped by what exactly happens to uranium ruthenium silicide (URu2Si2) at 17.5 kelvin (minus 256 degrees Celsius). By measuring heat capacity and other characteristics, they can tell it undergoes some type of phase transition, but that's as much as anyone can say with certainty. A team led by Brad Ramshaw used a combination of ultrasound and machine learning to narrow the possible explanations for what happens to this large sample of uranium ruthenium silicide when it enters its so-called "hidden order."