Researchers have discovered Devil Pines, a collection of electrons in metals that behave like massless waves. Credits: Grainger College of Engineering, University of Illinois Urbana-Champaign
Sixty-seven years after David Baines’ theoretical predictions, the elusive “devil” particle, a massless and neutral entity within solid matter, has been discovered in strontium ruthenates, underscoring the value of innovative research approaches.
In 1956, theoretical physicist David Baines predicted that electrons in solids could do strange things. Although electrons usually have mass and an electric charge, Baines asserted that electrons can combine to form compound particles that are massless, neutral, and do not interact with light. He called this theoretical particle “Satan”. Since then, it has been hypothesized to play an important role in the behavior of various minerals. Unfortunately, the same characteristics that make her so attractive have kept her from detection since she expected it.
After 67 years, a research team led by Peter Abamonte, a professor of physics at the University of Illinois Urbana-Champaign (UIUC), has finally discovered the elusive Devil of Pines. The researchers also report in the journal alamThey used a non-standard experimental technique that directly stimulated the electronic patterns of matter, allowing them to see devil signatures in the mineral strontium ruthenate.
“Devils have been speculated on theoretically for a long time, but they have never been studied by empiricists,” said Abamonte. “Actually, we weren’t looking for him. But it turned out we were doing the right thing, and we found it.”
Satan is elusive
One of the most important discoveries in condensed matter physics is that electrons lose their individuality in solids. Electrical interactions cause electrons to combine to form a collective unit. Given enough energy, electrons can form complex particles called plasmons with new charges and masses determined by fundamental electrical interactions. However, their mass is usually too large to be formed by plasmons with available energy at room temperature.
Baines found an exception. If a solid contained electrons in more than one energy band, as is the case with many metals, it was argued that its plasmons could combine in an out-of-phase pattern to form a new, massless, neutral plasmon: satanic. Since demons are massless, they can form with any energy, so they can live at any temperature. This has led to speculation that they have an important influence on the behavior of multiscale minerals.
The neutrality of demons meant that they left no mark in standard condensed matter experiments. “Most of the experiments were done using light and measuring optical properties, but electrically neutral means the demons don’t interact with light,” said Abbamonte. “A completely different kind of experimentation is required.”
An unexpected find
Abbamonte recalls that he and his collaborators studied strontium ruthenite for an unrelated reason: the metal is a high-temperature superconductor without being a superconductor. Hoping to find clues to why this phenomenon occurs in other systems, they conducted the first survey of the electronic properties of metals.
The research group led by Yoshi Maeno, a professor of physics at Kyoto University, collected high-quality metal samples that Abamonte and former graduate student Ali Hussein examined using energy loss spectroscopy of electrons with momentum resolving. This is a non-standard technique, and uses the energy from electrons released into the metal to directly observe the properties of minerals, including the plasmons that are formed. When the researchers sifted through the data, they found something unusual: the electron’s massless mode.
“At first, we didn’t know what it was,” recalls Hussain, who is now a research scientist at Quantinum. Satan does not belong in the mainstream. This possibility arose from the start, and we basically laughed it off. However, as we started to put things aside, we started to suspect that we had actually found Satan.
Edwin Huang, a UIUC postdoctoral researcher and condensed matter theorist, was finally asked to calculate the features of the electronic structure of strontium ruthenite. “Baines’ prediction of the presence of demons requires fairly specific conditions, and it’s not clear to anyone whether strontium ruthenite should have demons or not,” he says. “We had to do microscopic calculations to show what was going on. When we did, we found a particle consisting of two bands of electrons oscillating out of phase by the same number, just as Baines described.
incidentally to seek
According to Abbamont, it’s no coincidence that his group came across Satan “by accident.” He emphasized that he and his group used techniques that were not widely used on material that had not been well studied. It is believed that their discovery of something unexpected and important was the result of trying something different, not just luck.
“He talked about the importance of measuring things,” he said. “Most of the great inventions are not planned. Go find a new place and see what’s out there.”
References: “Watch Demon Pines as a 3D acoustic plasmon at Sr2ruo4Written by Ali A. Hussain, Edwin W. Huang, Matthew Mitrano, Melinda S. Rack, Samantha I. Rubik, Ziofi Gu, Hongbin Yang, Chanchal Su, Yoshiteru Maino, Bruno Ochoa , Tai Si Chiang, Philip E. Batson, Philip W. Phillips and Peter Abamonte, 9 Aug. 2023, Available Here. alam.
two: 10.1038/s41586-023-06318-8
Abamonte is a member of the Materials Research Laboratory at UIUC. Huang is a member of the Condensed Matter Theory Institute at UIUC.
Professors Philip Phillips from UIUC, Matteo Mitrano from Harvard University, Bruno Ochoa from the University of Oklahoma, and Philip Paston from Rutgers University contributed to this work.
Support has been provided by the US Department of Energy, the Japanese Association for the Advancement of Science, the National Science Foundation, and the Gordon and Betty Moore Foundation.
2023-08-28 21:56:53
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