The researchers found that defects provide protection for system symmetry

The researchers found that defects provide protection for system symmetry

The international research team used this acoustic network model to explore how intentional defects can protect system symmetry. Credit: Guancong Ma / Hong Kong Baptist University

An international research collaboration has discovered how to exploit certain flaws to protect confined power in audio systems. Their experimental approach provides a versatile platform for creating imperfections at will for further theoretical verification and improved wave control in other systems, such as light, according to lead researcher Yun Jing, associate professor of acoustics and biomedical engineering at Penn State.

The team published their findings in Physical Review Letters, the principal publication of the American Physical Society. The research was selected as “Editors’ Suggestion” and also appeared in an explanatory article published by APS.

The work concerns phonons, and perhaps their optical equivalent, photons, which can travel across certain boundaries in so-called topological networks without scattering. First discovered in condensed matter, such synapses are made of atoms that repeat in minute patterns, held together by the strength of their coupling devices — or how they bind together in such a way that a change in one partner can affect another. According to Jing, these materials are known to host topologically protected states, which remain unchanged even if the system has some defects.

Moving these desirable states beyond their restrictive limits into the bulk of matter could lead to new applications in sensing, Jing said. However, for some cases, such movement requires the introduction of new defects that often break the chiral symmetry of the system – an essential property that allows for a maximum of cases associated with the introduced defect. This means that state energy is as isolated as possible from the patterns that can reduce or disrupt it.

“Chironic symmetry means there is a symmetric spectrum: all modes in the system either come in pairs, with frequencies equidistant from zero frequency, or they have no partner and sit exactly at zero frequency,” Jing said, noting that the second case is extremely rare and only occurs in configurations Certain topological defects specifically in topological lattices, including one called unraveling. “But crucially, the topological defects—which are necessary to embed the desired state within the bulk of structureIt often disrupts chiral symmetry, which goes against the purpose of having a topological structure to begin with. ”

The researchers could have set inclinations obeying chiral symmetry, but they fell into the first symmetric spectrum category of evenly paired states located equally far from zero frequency. Co-author Vladimir A. Benalcazar, who was an Eberley Postdoctoral Fellow in the Penn State Department of Physics at the time of the research and is now a Moore Postdoctoral Fellow at Princeton University, hypothesized that because the detection states are related to the defect core, perhaps the detection symmetry itself could be considered To prevent states at zero frequency from disengaging.

To test this, the researchers engineered a honeycomb-shaped acoustic network as an analogue of the crystal lattice. According to Jing, it is much easier to engineer and remedy defects in an acoustic system than it is with crystalline materials. Using cylindrical cavities to represent atoms, the researchers created a defect by removing part of the honeycomb, acoustically excitating the speaker grille and measuring its acoustic response with a microphone. The states associated with the detection core are fixed at zero frequency, which Jing called the “characteristic frequency” that ensures the maximum of the maximum bound state. Frequency is considered privileged because it reduces the possibility of disturbances destroying the state associated with it.

“We decided to understand whether topological defects, such as aberrations, could be created to hunt for highly confined and protected acoustic patterns from perturbations,” Ben Alcazar said. “Our basic insight was that if we consider the symmetry of the point set in the detection, a pair of skew modes is prevented from coupling far from zero. to hesitate. This protective mechanism results from the interaction of the symmetry-protected topological phase of the crystal lattice, the topological charge, and the detection symmetry. ”

This is the first work empirically validating this protection States Jing said exist in the core of the disclosure. The audio network platform approach provides a new tool for researchers to create a diverse collection Disadvantages and their potential, according to the researchers, who said both theory and a platform other than acoustics could potentially be applied to testing and building controlled applications using Electromagnetic waves or quantum systems in condensed matter physics.


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more information:
Yuanchen Deng et al, Observation of degraded topological states of zero energy at regression in an acoustic lattice, Physical Review Letters (2022). DOI: 10.1103/ PhysRevLett.128.174301

the quote: Researchers Find Imperfections Provide Protection for System Symmetry (2022, May 20), Retrieved May 21, 2022 from https://phys.org/news/2022-05-imperfections-symmetry.html

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