David J. Thouless

David James Thouless was born 21 September 1934 in Britain and spent his career in the abstract country where physics meets pure mathematics. His theoretical work on topological phase transitions - the idea that matter can shift between states governed not by temperature alone but by deep geometric properties - arrived long before experimentalists could see it in action. The insight, developed alongside collaborators F. Duncan M. Haldane and J. Michael Kosterlitz, eventually earned the three the 2016 Nobel Prize for physics, and Thouless had already taken the 1990 Wolf Prize years earlier. He died 6 April 2019, his equations still humming inside quantum labs.