Demon Hunting: Physicists Confirm 67-Year-Old Prediction of Massless, Neutral Composite Particle
hubie writes:
Physicists confirm 67-year-old prediction of massless, neutral composite particle:
In 1956, theoretical physicist David Pines predicted that electrons in a solid can do something strange. While they normally have a mass and an electric charge, Pines asserted that they can combine to form a composite particle that is massless, neutral, and does not interact with light. He called this particle a "demon." Since then, it has been speculated to play an important role in the behaviors of a wide variety of metals. Unfortunately, the same properties that make it interesting have allowed it to elude detection since its prediction.
Now, a team of researchers led by Peter Abbamonte, a professor of physics at the University of Illinois Urbana-Champaign, have finally found Pines' demon 67 years after it was predicted. As the researchers report in the journal Nature, they used a nonstandard experimental technique that directly excites a material's electronic modes, allowing them to see the demon's signature in the metal strontium ruthenate.
"Demons have been theoretically conjectured for a long time, but experimentalists never studied them," Abbamonte said. "In fact, we weren't even looking for it. But it turned out we were doing exactly the right thing, and we found it."
Journal Reference:
Husain, A.A., Huang, E.W., Mitrano, M. et al. Pines' demon observed as a 3D acoustic plasmon in Sr2RuO4. Nature 621, 66-70 (2023). https://doi.org/10.1038/s41586-023-06318-8
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