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Tuesday, May 28, 2024

Wigner crystal. Evidence. Wigner's crystal was imaged for the first time

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Scientists have now presented direct evidence of the existence of the Wigner crystal. Although this unusual type of matter, consisting only of electrons, has been the subject of many experiments for decades, this is the first time it has been directly observed.

In the 1930s, the Hungarian physicist Eugene Wigner proposed a concept according to which the interaction between electrons can lead to their arrangement in a repeating pattern. According to his theory, this can occur at extremely low temperature and density and as a result of mutual repulsion of electrons.

“The Wigner crystal is one of the most fascinating quantum phases of matter, and has been the subject of numerous studies that have claimed to have found indirect evidence for its formation,” says Ali Yazdani, a professor of physics at Princeton University in New Jersey.

Lots of experiments

For a long time, the Wigner crystal remained in the sphere of theory. It was only thanks to experiments, the first of which were carried out in the 1970s, that speculation about its existence stopped and was instead proven. Over the following decades, scientists managed to conduct a series of subsequent, more advanced experiments, but none of them failed to observe the crystal.

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A team of scientists from Princeton University, taking into account the shortcomings of previous experiments, designed their own experiment, which was intended to image the crystal. And that's how it happened.

A tool called a scanning tunneling microscope was used for this purpose, which allows obtaining an image with atomic resolution. Two thin sheets of graphene were used, each just one atom thick. To reduce the kinetic energy of the electrons, the graphene was cooled to a fraction of a degree above absolute zero. The sample was exposed to a magnetic field. The material had to be impeccably pure to exclude the possibility of electron crystals forming due to its imperfections.

Image of a Wigner crystal obtained using a scanning tunneling microscopeYen-Chen Tsui, Princeton University

“We can see him”

– Our work provides the first direct images of this crystal. We have proven that it really exists and that we can see it, said Yen-Chen Tsu, one of the study's authors.

As Ali Yazdani said, “visualizing this crystal allows us not only to observe its formation, confirming many of its properties, but we can also study it in a way that could not be done in the past.”

As we read in a press release from the American university, the latest discovery, described in the journal Nature, “confirms the 90-year-old theory that “electrons can combine to create their own crystal-like formation without the need to combine around atoms.”

princeton.edu, newscientist.com, tvnmeteo.pl

Main photo source: Yen-Chen Tsui, Princeton University

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