At the University of Illinois, scientists have received the first practical proof of the existence of excitony. This is a stable state of bosons, which, under certain conditions, form a fundamentally new form of matter. Its existence and the term "exciton" itself were deduced by Bert Halperin in the 60s of the last century, but until now all this was related to the field of theoretical physics.
The world at the quantum level is very unusual. If an electron is excited at the edge of the valence band, it can move to an adjacent, empty band, leaving a "hole" in the valence region in its place. It becomes a quasiparticle, whose charge is positive, but for an electron it is negative - this pair is attracted and a boson is obtained. More precisely, this particular boson is called an "exciton", and their array is called an "excitony" by the medium.
Physicists Anshul Kogar and Mindy Rack used pulsed energy loss spectroscopy technology. They investigated pseudo-metal crystals of titanium diselenide dichalcogenide 1T-TiSe2, which were cooled to 190 degrees Kelvin (-83 ° C). As this temperature is approached, the metal entered the rarest state of a soft plasmon — the phase that precedes the appearance of excitonium.
And although the coveted new form of matter itself has not yet been obtained, the measurement data convincingly prove that this is possible. There are literally a few steps left. From the field of theoretical physics, scientists moved on to practical. And although they cannot predict how much benefit can be derived from exciton at this stage, the very work with it will be the impetus for the development of quantum physics.
The team of scientists from the University of Illinois, which is responsible for the discovery of excitony: Mindy Rack, Peter Abbamon and Anshul Kogar