Electrons do not have to come together around atoms, but they can also collect themselves in crystal-like structures.
The Wigner crystal is one of the most interesting quantum levels of matter. enter a tight, crystal-like structure, and this only happens when the electrons repel each other at low densities and extremely cold temperatures.
When we think of stable crystal structures, we usually mean that there is an attraction between atoms, but a Wigner crystal, which is made up entirely of electrons, relies entirely on repulsion electrons together state of matter for a long time.
The first experiments took place in the 1970s, when Bell Labs scientists created “classical” electronic crystals by spraying electrons on the surface of helium and found that they responded in a solid way like crystals. While the electrons in the experiment were far apart and behaved more like single particles than cohesive structures, real Wigner crystals do not follow the laws of physics familiar from everyday life, but instead follow the laws of quantum physics, where electrons behave Not as one. grain but like a wave.
Therefore, in the following decades, many experiments suggested ways to create quantum Wigner crystals, which greatly stimulated research progress, physicists discovered that they could use semiconductors to limit the movement of electrons to thin layers of atoms also causes electrons to orbit. But these experiments did not look directly at the Wigner crystal and could only infer its existence, or infer it indirectly from the way electrons flow through it. semiconductor.
First direct observation of Wigner crystals
The Princeton team decided to directly image the Wigner crystals using a scanning tunneling microscope (STM), a device that relies on quantum tunneling technology instead of light to visualize the crystals. In the experiment, the researchers cooled the sample to a very low temperature and applied a magnetic field perpendicular to the sample to create a two-dimensional gas (2DEG) system in the graphene thin layer the electrical density between the two layers can be changed.
The team also found that while the density is changed, the electrons spontaneously form ordered crystals.
Placing electrons in a magnetic field hinders their movement, thus increasing the chance of crystallization first, the electrons are far apart, arranged in a disorderly manner, or -organized The force begins to push each other away, but due to the limited density, the electrons cannot be separated infinitely, and finally a dense and regular lattice structure is formed, with each local electricity in a particular place.
When this transformation occurred, the researchers directly observed the existence of Wigner crystals for the first time through STM microscopy.
Wigner crystals are also the best for electron density. If the density is too low, electrons push each other away from a point”.
The researchers also found other interesting phenomena, such as the position of each electron in the crystal lattice, but there is a degree of “blurring” in the image. This phenomenon is related to the Heisenberg uncertainty principle and indicates a Wigner crystal. Its quantum properties deserve more research in the future.
new paperPublished in the journal Nature.
(Source of first image:Princeton University)
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