Actively controllable topological phase transition in phononic beam systems

Abstract

Topological insulators, which allow edge or interface waves but forbid bulk waves, have revolutionized our scientific cognition of acoustic/elastic systems. Due to their nontrivial topological characteristics, edge (interface) waves are topologically protected against defects and disorders. This superior and unique characteristic could lead to a wealth of new opportunities in applications of quantum and acoustic/elastic information processing. However, current acoustic/elastic topological insulators are still at an infancy stage where the theory and prediction only work in laboratories and there are still many problems left open before promoting their practical applications. One of the apparent disadvantages is their narrow working frequency range, which is the main concern in this paper. We design a one-dimensional phononic beam system made of a homogeneous epoxy central beam sandwiched by two homogeneous piezoelectric beams, and covered with extremely thin electrodes, periodically and separately placed. These electrodes are connected to external electric circuits with negative capacitors. We show that a topological phase transition can be induced and tuned by changing the values of the negative capacitors. It follows that the working frequency of the topologically protected interface mode can be widely changed, such that the working frequency range of the topological insulator can be considerably 'broadened'. This intelligent topological device may also find wide applications in intelligent technologies that need controllable information processing of high precision.

Defect‐Adjusted Valley Edge States and Rainbow Trapping of Elastic Waves in 2D Topological Phononic Crystals

“…For example, Sui et al [ 26 ] designed a new 2D magnetoelastic PnC plate to tune the pseudo‐spin Hall edge mode by applying an external static magnetic field and demonstrated the reconfigurable propagation path and topological robustness of the edge state through numerical simulations. Zhou et al [ 27 ] actively controlled the characteristic frequency of the resulting topologically protected edge pattern by applying an appropriate external voltage. Kurganov et al [ 28 ] proposed a topological edge state manipulation method based on temperature modulation.…”

Tunable topological interface states and resonance states of surface waves based on the shape memory alloy

“…Meanwhile, due to the main disadvantages of narrow working range with the single frequency points for the TIS in the previous 1D topological PnC systems, a theme of studying tunable TIS to realize the controllable and programmable wave manipulation has drawn increasing attention. Zhou et al [31][32][33] proposed a 1D active topological PnCs made of a homogeneous central epoxy central beam/rod sandwiched by two piezoelectric beams/rods, in which the tunable TIS could be realized by adjusting the capacitors of the periodic electric circuits. Chen et al [34] demonstrated low-frequency tunable TIS for longitudinal wave by utilizing soft topological phononic crystals, in which the tunability is achieved based on the applied axial force field.…”

Tuning of subwavelength topological interface states in locally resonant metastructures with shunted piezoelectric patches

“…Then, Spadoni et al constructed the two-dimensional periodic piezoelectrical meta-plate to analyze wave propagation control of the shunted circuit 33 , which was confirmed experimentally 34 . Zhou et al proposed a periodic piezoelectric rod 35 and beam metastructure 36 to obtain tunable topological interface states for longitudinal and flexural elastic waves via employing electrical shunting circuits, respectively. The locally resonant sub-structure can be utilized to realize the lower frequency bandgap in the sub-wavelength region.…”