A new form of matter called excitonium - which was first theorised almost 50 years ago, has now been discovered by researchers.
Physics professor Peter Abbamonte and his team of researchers from University of California and other colleagues from University of Illinois, Berkeley, and University of Amsterdam worked together to prove the existence of excitonium.
The scientists discovered that excitonium is a rather exotic condensate that exhibits macroscopic quantum phenomena like a superconductor or a superfluid.
The researchers studied non-doped crystals of a transition metal— dichalcogenide titanium diselenide (1T-TiSe2) and discovered that excitonium is a rather exotic condensate that exhibits macroscopic quantum phenomena like a superconductor or a superfluid. It is made up of excitons, particles that are formed in a very strange quantum mechanical pairing, the scientists noted.
When an electron, seated at the edge of the crowded-with-electrons valence band in a semiconductor, gets excited and jumps over the energy gap to the otherwise empty conduction band, it leaves behind a “hole” in the valence band. That hole behaves as though it were a particle with positive charge, and it attracts the escaped electron. When the escaped electron with its negative charge, pairs up with the hole, the two remarkably form a composite particle, a boson - an exciton.
Until now, the researchers had not had the experimental tools that were required to differentiate with certainty whether they were detecting excitonium or another similar phase of matter. Abbamonte and his team of scientists used a novel technique called momentum-resolved electron energy-loss spectroscopy (M-EELS) for the study. With their new technique, the scientists were able to measure collective excitations of the low-energy bosonic particles, the paired electrons and holes.
“Ever since the term ‘excitonium’ was coined in the 1960s by Harvard theoretical physicist Bert Halperin, physicists have sought to demonstrate its existence,” said Peter Abbamonte, professor at University of Illinois. “Theorists have debated whether it would be an insulator, a perfect conductor, or a superfluid—with some convincing arguments on all sides.”
The findings that hold great promise for unlocking further quantum mechanical mysteries, was published in the journal Science and can be read here.