MATHEMATICAL SCIENCES

Acoustic Sigmin sub-patterns are observed in local resonance structures


The team of Wu Hongwei, associate professor of the School of Mechanics and Optoelectronic Physics of Anhui University of Science and Technology, carried out theoretical research and experimental observations on the vector characteristics and distribution regulation of velocity vector fields in acoustic systems, realized the Sigmin sub-mode distribution and local regulation of velocity fields, effectively expanded the way to manipulate vector fields, and provided more regulatory freedom for the future realization of high-speed, high-density acoustic information storage and transmission. The relevant research results were recently published in Applied Physics Letters.

Experimental observation of local regulation of acoustic Sigmin sub-mode Courtesy of Anhui University of Science and Technology

The Sigminon was first proposed by British physicist Tony Skyrme in high-energy physics as a topological soliton. In recent years, people have observed the Sigmin sub-pattern in different physical systems (including Bose Einstein condensates, magnetic materials, optical systems, etc.), and developed a variety of Sgmin sub-distributions, which are expected to replace traditional computer hard disks and achieve ultra-compact data storage.

“As one of the classic waves, sound waves play an important role in daily life and production. With the help of acoustic metamaterial design, the velocity field distribution of special sound waves can realize the control of sound wave transmission, so as to promote the application of sound waves in biomedicine, sensing detection, and information transmission and storage. Wu Hongwei introduced to China Science News.

In recent years, due to its special real space topological protection and great application prospects, the Sgemin submode has become a hot spot and frontier direction in research in different branches of physics. However, sound waves have historically been considered spinless scalar fields compared to vector fields such as optics. Until recently, it was recognized that structure-borne sound fields in acoustic systems can produce vectors with rotational velocity fields. Therefore, studying the Sigmin submode distribution of the velocity field in the acoustic system is not only of great significance for the actual transmission and storage of sound waves, but also has certain scientific value for understanding the vector characteristics of sound waves.

Wu Hongwei’s team took the lead in the field of acoustics to carry out the research of the Sigmin sub-mode, designed the Archimedes spiral sub-wavelength superstructure, realized the local acoustic Sgmin sub-mode, and realized the data storage of acoustic signals. It is found that this helical structure can not only support multi-frequency Sigmin sub-mode, but also have the advantages of easy excitation and simple sample production.

“Our research found that this physical mechanism comes from the grooves on the surface of the metastructure that have a binding effect on the sound waves, forming acoustic surface waves with high propagation wave vectors, and then interfering on the structural surface to produce a special distribution of sound velocity vector fields.” Wu Hongwei said.

The traditional Sigmin submode can usually be divided into Néel type, Bloch type, inverse Sgmin sub-pattern, etc. according to the vector field distribution type, and these types of Sigmin submode have fixed vector field distribution characteristics. In order to further manipulate the vector field distribution of the Sigmin submodel, the research group further proposes a gradient superstructure scheme on the basis of the previous work to realize the local regulation of the vector field inside the Néel Sigmin submode and produce a compact or expanded vector field distribution. By 3D printing the actual concave, flat, and convex samples, the velocity field distribution of the Sigmin sub-mode of contraction, flattening, and expansion was actually observed experimentally. This method of internal local manipulation of the Sigmin sub-mode not only has the same regulatory effect on the Néel type mode, but also on other types of patterns, and still maintains the topological protection of the Sigmin sub-mode. The research results effectively expand the way to manipulate vector fields, and provide more degrees of freedom for regulating the distribution of velocity vector fields.

The reviewer said: “The author proposes a new method in the field of acoustics to generate Néel-type Sigmin sub-mode, and observes the local manipulation and topological protection characteristics of Sigmin sub-mode through experiments, which is of great significance in acoustic information transmission and storage.” (Source: Wang Min, China Science News)

Related paper information:https://doi.org/10.1063/5.0145611



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