Jul, 2021 - By WMR
A group of theoretical physicists predicted how the effect might manifest itself in the observed excitons' excitation frequencies.
A crystal comprised entirely of electrons has been developed by researchers at ETH Zurich. The structures have been postulated for decades, but this is the first time they've been validated in a lab setting. Electrons, in most cases, behave like a fluid, flowing spontaneously over a substance. However, theoretical physicist named Wigner expected in 1934 that a collection of electrons may crystallise into a solid form under certain conditions, resulting in the Wigner crystal phase.
The types of particles in crystalline substances, as well as the types of chemical bonding that occurs between them, can be used to describe them. Ionic, metallic, covalent network, and molecular crystals are the four types of crystals.
To do so, the appropriate balance between two forces that effect electrons must be struck: electrostatic repulsion and energy of motion. At the end it is the more strong effect, allowing electrons to bounce around at random, but Wigner projected that if the latter could be decreased sufficiently, disgust could take over, securing the electrons into a uniform lattice.
But it turned out to be more difficult than it seems. To eliminate outside impact on electron movement, the density of electrons must be reduced beyond a certain point, they must be confined in a "trap," and they must be cooled almost to absolute zero. Scientists at ETH Zurich have now completed all of the conditions for making a Wigner crystal. They employed a one-atom-thick film of molybdenum diselenide to confine the electrons, essentially limiting their travel to two dimensions.
The team put this material between two graphene electrodes and applied a precise voltage to regulate the several number of electrons in the semiconductor. Thus, the entire system was chilled to near-absolute zero temperatures.
However, viewing it was a different storey; the difference between the electrons is very tiny, that microscopes can't even see it. Previous attempts to generate Wigner crystals had to rely on indirect means, such as current changes, to detect them.