A Bose Einstein condensation, a state predicted by Einstein almost a century ago, is the unique state of matter in which certain types of atoms can exist in temperatures close to absolute zero. The Bose Einstein condensate is one of the simplest systems in nature. The Bose Einstein condensation shows the phenomenon of superfluity and superconductivity.
The Bose Einstein condensate is a gas of atoms so dense and cold that their matter waves lose their individuality and condense into a macroscopic coherent superatom wave. Atomic Bose Einstein condensation very often occurs at a temperature near absolute zero. However, excitons are expected to exhibit the same phenomenon at temperatures that are millions of times higher.
Remarkably, this is a range of temperatures whereat Butov and his team have observed the onset of exciton coherence. Excitons are particles that can be created inside of semiconductors -- in this case, gallium arsenide, the material used to make transistors in cell phones. One can make excitons, or excite them, by shining bright light on a semiconductor. The light kicks electrons out of the atomic orbitals they normally occupy inside of the material. This creates a negatively charged "free" electron and a positively charged "hole."