The first ever photograph of a Wigner Crystal, a bizarre honeycomb-pattern material that is entirely made of electrons, has been taken by physicists.
Eugene Wigner, a Hungarian physicist, first described this crystal in 1934. However scientists have had to wait more than eight decades to get a look at "electronice". This first image shows electrons being pressed together to form a tight pattern, similar to tiny blue butterflies wings or pressings of an alien clover.
Researchers behind the study, which was published in Nature on September 29th, stated that although it is not the first time that Wigner crystals have been created or their properties examined, the visual evidence that they collected is the strongest proof yet of its existence.
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Feng Wang, a University of California physicist, said, "If you claim you have an electron-crystal, show me the crystal."
Ordinary conductors such as silver and copper or semiconductors such as silicon have electrons that move so fast they can barely interact with one another. At very low temperatures they slow down and the repulsion of the negatively charged electrons takes over. To minimize their energy consumption, the once mobile particles come to a halt and form a honeycomb-like pattern.
The researchers captured electrons between two layers of atom-thick tungsten semiconductors, one tungsten dioxide and the other tungsten elenide to see the process in action. After applying an electric field to the gap to eliminate any potential disruptive excess electrons they had, the researchers chilled the electron sandwich to 5 degrees above absolute 0. The once-fast electrons stopped moving and settled into the repeating structure a Wigner Crystal.
To view the new crystal, researchers used a scanner tunneling microscope (STM). STMs work by placing a small voltage across a very sharp tip of metal before it is placed just above a material. This causes electrons to jump down to the surface of the material from the tip. Researchers can measure current flowing into the surface at each point to get a picture of Braille-like contours. This will determine the rate electrons jump from the tip.
The current from the STM was too strong for the delicate electron-ice and "melted" it on contact. The researchers placed a single-atom layer graphene above the Wigner Crystal to stop it from melting. This allowed the crystal to interact and leave an impression that the STM could read like a photocopier. The STM took the first photograph of the Wigner Crystal by completely tracing the graphene image, and proved its existence beyond doubt.
Scientists now have strong evidence that Wigner crystals are real. They can now use these crystals to probe deeper questions about how electrons interact, such as how the crystals form honeycomb arrangements and how they melt. These answers will give scientists a rare insight into the most mysterious properties of tiny particles.
Original publication on Live Science
