An interdisciplinary team led by Boston College physicists has discovered a new particle, or previously undetectable quantum excitation, known as axial Higgs mode, a magnetic relative of the mass-defining mass of the Higgs boson particle. the journal Nature. Credit: Nature
Materials containing axial Higgs mode could serve as quantum sensors to evaluate other quantum systems and help answer persistent questions in particle physics.
According to the standard model of particle physics, the best current theory of scientists to describe the most basic building blocks in the universe, particles called quarks (which form protons and neutrons) and leptons (which include electrons) are all known matter. . Strength-bearing particles, which belong to a wider group of bosons, influence quarks and leptons.
Despite the success of the Standard Model in explaining the universe, it has its limitations. Dark matter and dark energy are two examples, and it is possible that new particles, yet to be discovered, can solve these riddles.
Today, an interdisciplinary team of scientists led by Boston College physicists announced that they had discovered a new particle, or previously undetectable quantum excitation, known as the axial Higgs mode, a magnetic relative of the mass-defining mass of the Higgs boson particle. . The team published its report today (June 8, 2022) in the online issue of the journal Nature.
Detection a decade ago of the much-sought-after Higgs boson became central to mass understanding. Unlike its father, axial Higgs mode has a magnetic moment, and this requires a more complex form of theory to explain its properties, said Boston College physics professor Kenneth Burch, lead co-author of the report. Axial Higgs mode detected by Quantum path interference to RTe3.
Theories that predict the existence of this mode have been invoked to explain “dark matter,” the almost invisible material that makes up much of the universe, but is only revealed by gravity, Burch said.
The Higgs boson is the fundamental particle associated with the Higgs field, a field that gives mass to other fundamental particles such as electrons and quarks. The mass of a particle determines how much it resists changing its velocity or position when it encounters a force.
While the Higgs boson was revealed by experiments in a massive particle collider, the team focused on RTe3, or rare earth tritellure, a well-studied quantum material that can be examined at room temperature in an experimental “table” format.
“It’s not every day that you find a new particle on the table,” Burch said.
RTe3 has properties that mimic the theory that produces the axial Higgs mode, Burch said. But the central challenge in finding Higgs particles in general is their weak coupling to experimental probes, such as light beams, he said. Similarly, revealing the subtle quantum properties of particles often requires rather complex experimental configurations, which include huge magnets and high-power lasers, while cooling samples to extremely cold temperatures.
The team reports that it overcame these challenges through the exclusive use of light scattering and the proper choice of the quantum simulator, essentially a material that mimics the desired properties for the study.
Specifically, the researchers focused on a compound that has long been known to possess a “charge density wave,” that is, a state where electrons self-organize with a density that is periodic in space. dir Burch.
The fundamental theory of this wave mimics the components of the standard model of particle physics, he added. However, in this case, the charge density wave is quite special, it rises well above room temperature and involves the modulation of both charge density and atomic orbits. This allows the Higgs boson associated with this load density wave to have additional components, i.e. it could be axial, i.e. it contains angular momentum.
In order to reveal the subtle nature of this mode, Burch explained that the equipment used light scattering, where a laser shines on the material and can change color as well as polarization. The color change results from the light created by the Higgs boson in the material, while the polarization is sensitive to the symmetry components of the particle.
In addition, by properly choosing the incident and outgoing polarization, the particle could be created with different components, such as absent magnetism or an upward pointing component. Taking advantage of a fundamental aspect of quantum mechanics, they used the fact that for a configuration, these components are canceled. However, they add for a different configuration.
“As such, we were able to reveal the hidden magnetic component and demonstrate the discovery of the first axial Higgs mode,” Burch said.
“Axial Higgs detection was predicted in high-energy particle physics to explain dark matter,” Burch said. “However, it has never been observed. Its appearance in a condensed matter system was completely startling and heralds the discovery of a new state of broken symmetry that was unforeseen. Unlike the extreme conditions that they are usually required to observe new particles, this was done at room temperature in a desktop experiment where we get a quantum control of the mode just by changing the polarization of the light “.
Burch said the seemingly accessible and simple experimental techniques deployed by the team can be applied to study in other areas.
“Many of these experiments were done by a graduate student in my lab,” Burch said. “The approach can be applied directly to the quantum properties of many collective phenomena, including modes in superconductors, magnets, ferroelectrics, and charge density waves. In addition, we carry out the study of quantum interference in materials with phases. correlated and / or topological at room temperature overcoming the difficulty of extreme experimental conditions.
In addition to Burch, co-authors of the Boston College report included undergraduate student Grant McNamara, recent doctoral student Yiping Wang, and postdoctoral researcher Md Mofazzel Hosen. Wang won the American Society of Physics’ best thesis in magnetism, in part because of his work on the project, Burch said.
Burch said it was crucial to take advantage of the wide range of expertise among researchers at BC, Harvard University, Princeton University, the University of Massachusetts, Amherst, Yale University, Washington University and the Chinese Academy. of Sciences.
“This shows the power of interdisciplinary efforts to reveal and control new phenomena,” Burch said. “Not every day optics, chemistry, physical theory, materials science and physics come together in one job.”
Reference: Yiping Wang, Ioannis Petrides, Grant McNamara, Md Mofazzel Hosen, Shiming Lei, Yueh-Chun Wu, James L. Hart, Hongyan Lv, Jun Yan, Di Xiao, Judy J. Cha, Prineha Narang, Leslie M. Schoop and Kenneth S. Burch, June 8, 2022, Nature.DOI: 10.1038 / s41586-022-04746-6
Funding: US Department of Energy