Theorized 50 years ago, scientists have finally discovered a new form of matter called excitonium. This condensate is made up of excitons.
Excitons are a type of boson formed in a semiconductor. When an electron on the edge of a semiconductor’s valence band gets excited, it can cross the band gap into the conduction band, which is empty. When it does, it leaves a “hole” in the valence band, which itself becomes a quasiparticle with a positive charge. The positively-charged hole and the negatively-charged electron are attracted to each other and together form a kind of boson known as an exciton.
