Spontaneous Bose-Einstein condensation of excitons

Excitons are pairs of electrons and holes inside a solid material that together behave like a single particle. It has long been suspected that when many such excitons exist in the same piece of matter, they can form a single giant quantum state called a Bose-Einstein condensate – the same process which is responsible for a metal losing all its electrical resistance when it becomes a superconductor, for example. However, actually proving that Bose-Einstein condensation of excitons occurs in any real material has been a challenge for physicists for decades. An experiment done at the University of Illinois at Urbana-Champaign, carried out in collaboration with UvA-Institute of Physics researcher Jasper van Wezel, has uncovered evidence that this elusive state of matter really does exist. Their results were published in Science this week.