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Abstract
In the present work, the acoustic band structure of a two-dimensional phononic crystal (PC) containing an organic ferroelectric (PVDF-polyvinylidene fluoride) and topological insulator (SnTe) was investigated by the plane-wave-expansion (PWE) method. Two-dimensional PC with square lattices composed of SnTe cylindrical rods embedded in the PVDF matrix is studied to find the allowed and stop bands for the waves of certain energy. Phononic band diagram ω = ω(k) for a 2D PC, in which non-dimensional frequencies ωa/2πc (c-velocity of wave) were plotted vs. the wavevector k along the Г–X–M–Г path in the square Brillouin zone shows five stop bands in the frequency range between 10 and 110 kHz. The ferroelectric properties of PVDF and the unusual properties of SnTe as a topological material give us the ability to control the wave propagation through the PC over a wide frequency range of 103–106 Hz. SnTe is a discrete component that allows conducting electricity on its surface but shows insulator properties through its bulk volume. Tin telluride is considered as an acoustic topological insulator as the extension of topological insulators into the field of “topological phononics”.
Public Interest Statement
Phononic crystals (PCs) are composite materials that are artificially manufactured structures with special properties regarding wave propagation, known as acoustic metamaterials. The most interesting aspect of such materials arises from the presence of phononic band gaps (PBGs). It is important to understand phononic behavior of polymeric materials combined with topological materials, such as PVDF/SnTe. These types of structures can be regarded as smart materials and be utilized for energy harvesting and they may be useful to the improvements in the design of acoustic phononic crystals. Many smart structures are periodically made up of two or more distinct constituents, and due to their combined properties, they may have potential engineering applications such as vibration/noise insulation, waveguides, or acoustic wave filtering. They provide some perspectives in a way for designing acoustic filters or insulators.
Acknowledgment
The author (Ekmel Ozbay) acknowledges partial support from the Turkish Academy of Sciences.
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Amirullah M. Mamedov
Dr Amirullah M Mamedov, Emeritus Professor and Seniour Researcher, is in Nanotechnology Research Center (NANOTAM) at Bilkent University in Turkey. He received his PhD Degree in Solid State Physics at the Ioffe Phys. Techn. Institute Academy Sci. of the USSR (1974, St. Petersburg) and received his Doctor of Habilitatus (Doctor of Sciences) in Optics and Spectroscopy at the Latvian State University (1984, Riga, Latvia). His current research interest focuses on Nonlinear Optics, Electro-Optics and Guidance Systems, Metamaterials and Nanostructures, and Electronic Properties of Topological insulators and Ferroelectric Materials. The research reported in this paper relates to understanding of complex structures to create materials with enhanced properties that can be tailored to a particular application.