67-year-old particle physicist’s bizarre prediction has finally been confirmed

The researchers discovered Devil Pines, a collection of electrons in metals that behave like massless waves. Contributors: Granger College of Engineering, University of Illinois, Urbana-Champaign.

Sixty-seven years after David Baines’ theoretical predictions, an elusive “devil” particle, a massless and neutral entity within a solid, has been discovered in strontium ruthenates, highlighting 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 electrical charge, Baines argued that electrons can combine to form complex particles that are massless, neutral, and do not interact with light. He called this theoretical particle “Satan”. It has since been suggested that it plays an important role in the behavior of various minerals. Unfortunately, the same characteristics that make her so attractive keep her from being discovered, even though she expected it to be.

After 67 years, a research team led by Peter Abamonte, professor of physics at the University of Illinois Urbana-Champaign (UIUC), has finally discovered the elusive Pine Devil. The researchers also report in the journal naturalThey used a non-standard experimental technique that directly stimulated the electronic structures of matter, allowing them to see traces of the devil in the mineral strontium ruthenate.

“Devils have been theorized for a long time, but they have never been studied by empiricists,” Abamonte said. “We weren’t really looking for him. But it turned out that 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 produced by plasmons with available energy at room temperature.

Baines found an exception. If a solid contains electrons in more than one energy band, as happens with many metals, it has been argued that its plasmons can combine in antiphase to form a new, massless, neutral plasmon: satanic. Because demons have no mass, they can form with any energy, so they can live at any temperature. This has led to the suggestion that they have an important influence on the behavior of multiscale minerals.

The neutrality of the demons meant that they left no traces in standard condensed matter experiments. “Most of the experiments have been done using light and measuring optical properties, but electrical neutrality means demons don’t interact with light,” Abbamonte said. “Completely different experiments are required.”

unexpected find

Abbamonte recalls that he and his colleagues studied strontium ruthenite for an unrelated reason: the metal is a high-temperature superconductor, but it is not a superconductor. Hoping to find a clue as to why this phenomenon occurs in other systems, they conducted the first study of the electronic properties of metals.

The research team, led by Yoshi Maeno, professor of physics at Kyoto University, collected high-quality metal samples, which Abamonte and former graduate student Ali Hussain examined using momentum-resolved electron energy loss spectroscopy. This is an unconventional technique that uses the energy of electrons released into a metal to directly observe the properties of minerals, including the resulting plasmons. When the researchers analyzed the data, they found something unusual: a massless electron mode.

“At first we didn’t know what it was,” recalls Hussain, who is now a research assistant at Quantinum. Satan does not belong to the mainstream. This opportunity arose from the very beginning, and we, in fact, laughed it off. However, as we began to put everything aside, we began to suspect that we had actually found Satan.

Edwin Huang, a UIUC postdoctoral fellow 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 quite specific conditions, and it’s not clear to anyone whether strontium ruthenites should have demons or not,” he says. “We had to do microscopic calculations to show what was going on. When we did this, we found a particle consisting of two bands of electrons oscillating out of phase by the same number, as described by Baines.

by the way search

According to Abbamont, it was no coincidence that his group encountered Satan “by chance.” He emphasized that he and his group used methods that were not widely used on little known material. It is believed that their discovery of something unexpected and important was the result of trying something else, and not just luck.

“He talked about the importance of measuring things,” he said. “Most great inventions are not planned. Go find a new place and see what’s there.”

Link: “See Demon Pines as a 3D Acoustic Plasmon in Sr.2roux4Screenwriter: Ali A. Hussain, Edwin W. Huang, Matthew Mitrano, Melinda S. Rack, Samantha I. Rubik, Ziofi Gu, Yang Hongbin, Chanchal Su, Yoshiteru Maino, Bruno Ochoa, Tai Si Chan, Philip E. Batson, Philip W. Phillips and Peter Abamonte, 9 August 2023, available here. natural.
doi: 10.1038/s41586-023-06318-8

Abamonte is a member of the UIUC Materials Research Laboratory. Huang is a member of the Institute for Condensed Matter Theory at UIUC.

Professors Philip Phillips of UIUC, Matteo Mitrano of Harvard University, Bruno Ochoa of the University of Oklahoma, and Philip Paston of Rutgers University contributed to this work.

Support was provided by the US Department of Energy, the Japan Association for the Advancement of Science, the National Science Foundation, and the Gordon and Betty Moore Foundation.

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