Electrons typically move at very high speeds through unbound matter. In 1934, physicist Eugene Wigner hypothesized that free electrons could form a strange quantum state of matter at very low density and low temperature. Thus, electrons create a crystalline lattice, which later became known as the Wigner crystal. Three years ago, indirect evidence for the existence of this quantum state of matter was obtained, and earlier this year, physicists made its first images. Now, physicists have captured the first direct images of a new state of this form of matter, referred to as the Wigner molecular crystal. The research results were published in the journal Science, as reported by Phys.
A crystal is one way that atoms can be arranged in solid matter. In this case, atoms form bonds in the shape of a crystalline lattice with a repeating pattern. Wigner believed that electrons at low density and low temperature could also freeze into a similar arrangement. According to the physicist, these electron crystals should operate according to quantum mechanics rather than classical physics. Therefore, Wigner crystals represent a quantum form of matter.
For many years, physicists attempted to obtain direct images of the molecular Wigner crystal, but they were unsuccessful. While electrons in Wigner crystals are arranged like honeycombs, in molecular Wigner crystals, they have a slightly different structure made up of artificial "molecules" consisting of two or more electrons.
Using a scanning tunneling microscope, which employs quantum tunneling to study materials at the atomic and subatomic levels, physicists have obtained direct images of this new quantum state of matter for the first time.
To achieve this, scientists created a nanomaterial known as twisted moiré superlattice of tungsten disulfide (tWS2). The nanomaterial was produced by applying a thin double layer of tungsten disulfide onto a layer of hexagonal boron nitride that is 49 nanometers thick.
During the study, physicists found that the introduction of electrons onto tWS2 fills each cell of the material, which is 10 nanometers wide, with just two or three electrons. As a result, these cells formed a large array of "molecules," leading to the creation of the Wigner molecular crystal.
According to the scientists, the interactions between quantum mechanics and the interactions among electrons transfer the electrons into the state of Wigner molecules.
Now, physicists aim to explore this new quantum state of matter further to understand how it can be utilized.