Researchers at the University of Illinois have announced the existence of a new form of matter called excitonium.
This material is made up of a kind of boson, a composite particle that could allow the matter to act as a superfluid, superconductor, or even as an insulating electronic crystal.
The hole is positively charged and the electron is negatively charged, so it is possible to create a bound state between the two, with the electron orbiting the hole, instead of falling back in. This bound state is the exciton, which is the building block of excitonium.
There are five known states of matter: solids, liquids, gases, plasma and Bose-Einstein condensates.