![]() “Crucially, however, topological defects - which are necessary to embed the desired state within the bulk of the lattice - often disrupt chiral symmetry, which defeats the purpose of having a topological structure to begin with.” “Chiral symmetry implies the existence of symmetric spectrum: all modes in the system come either in pairs, with frequencies equidistant from zero frequency, or they do not have a partner and sit exactly at zero frequency,” Jing said, noting that the second case is exceedingly rare and only occurs in particular configurations of topological defects specifically in topological lattices, including one called a disclination. This means the state’s energy is as isolated as possible from modes that could diminish or disrupt it. However, for some states, such movement requires introducing new defects that often break the system’s chiral symmetry - a key property that allows maximal confinement of the states bound to the introduced defect. Moving these desired states beyond their restrictive boundaries to the bulk of the material could lead to new applications in sensing, Jing said. According to Jing, these materials are known to host topologically protected states, which remain unchanged even if the system contains certain imperfections. Such lattices were first discovered in condensed matter, in which materials consist of atoms repeating in precise patterns, held together through the force of their couplings - or how they are bound to one another in such a way that a change in one partner can influence the other. The work relates to phonons, and potentially their optical equivalent, photons, which can navigate specific boundaries in so-called topological lattices without scattering. The research was selected as the “Editors’ Suggestion” and was also featured in a commentary article by APS. The team published their results in Physical Review Letters, the flagship publication of the American Physical Society. Their experimental approach provides a versatile platform to create at-will defects for further theoretical validation and to improve control of waves in other systems, such as light, according to principal investigator Yun Jing, associate professor of acoustics and of biomedical engineering at Penn State. An international research collaboration has discovered how to exploit certain defects to protect confined energy in acoustics systems. Credit: Guancong Ma/Hong Kong Baptist University Researchers find imperfections provide protection for system symmetry The theory-validating work has implications for optimizing control of bound states, researchers say ![]() Researchers used this acoustic lattice model to investigate how intentional defects could protect the system's symmetry.
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