Electrons are usually seen darting around their atoms, but a team of physicists has now imaged the particles in a very different state: nestled together in a quantum phase called a Wigner crystal, without a nucleus at their core.
The phase is named after Eugene Wigner, who predicted in 1934 that electrons would crystallize in a lattice if certain interactions between them were strong enough. The current team used high-resolution scanning tunneling microscopy to directly image the predicted crystal. their research is published this week in nature.
“The Wigner crystal is one of the most fascinating quantum phases of matter predicted and the subject of numerous studies claiming to have found at best indirect evidence for its formation,” said Ali Yazdani, a physicist at Princeton University and the lead researcher Author of the study at a university release.
Electrons repel each other and like to avoid each other. In the 1970s, a team from Bell Laboratories Created an electron crystal by spraying the particles onto helium, they observed how the electrons behaved like a crystal. But this experiment remained stuck in the classical realm. The latest experiment produced a “true Wigner crystal,” according to the team, because the electrons in the lattice acted as a wave rather than as individual particles glued together.
Wigner suspected that this quantum phase of electrons would occur due to the mutual repulsion of the particles and not in spite of it. However, this would only happen in very cold temperatures and low density conditions. In the new experiment, the team placed electrons between two sheets of graphene, which were thoroughly cleaned of material defects. They then cooled the samples and applied a magnetic field perpendicular to them. The highest magnetic field strength was 13.95 Tesla and the lowest temperature was 210 millikelvin. When the electrons are placed in a magnetic field, their movement is further restricted, making them more likely to crystallize.
“There is an inherent repulsion between electrons,” Minhao He, a researcher at Princeton University and co-first author of the paper, said in the same press release. “They want to push each other away, but in the meantime the electrons cannot be infinitely far apart because of the finite density. The result is that they form a tightly packed, regulated lattice structure, with each of the localized electrons occupying a specific space.”
The team was surprised that the Wigner crystal remained stable over a longer range than expected. However, at higher densities the crystalline phase gave way to one Electron fluid. Next, the researchers want to image how the Wigner crystal phase gives way to other electron phases under a magnetic field.
These are exciting days to study exotic materials take a close look at the second sound of heat To Time crystals that last longer than ever before. By studying the matter at its ends, physicists will better understand the stuff that makes up our universe and the mysterious laws that govern it.
More: Physicists are finally observing an exotic state of matter first predicted in 1973