Active topological phase transitions in high-order elastic topological insulators driven by pneumatic methods and liquid metals

Abstract

Active topological phase transitions widely occur in active matters and biological systems, such as developing embryos. Since the discovery of the intriguing bulk-boundary effects of topological insulators in Hermitian and non-Hermitian systems, various electric, optical, acoustic, and mechanical topological metamaterials with efficient energy transmission and robust defect-immunization have been designed. To date, however, it remains a challenge to precisely and fast manipulate the topological phase transitions in elastic topological insulators. In this paper, on the basis of theoretical analysis and numerical simulations, we propose an active strategy to achieve this aim through a combination of pneumatic actuation and liquid metals. The proposed method can precisely tune the connecting stiffness and vertex mass in the tight Su–Schrieffer–Heeger model. Thus, we realize the effective and fast control of topological phase transitions and elastic wave bandgap switching. We also uncover the active spinning bulk-boundary effects and higher-order topological states in the elastic topological insulators, demonstrating the high effectiveness and practicability of the proposed method. In addition, the differences between the 1D edge and 0D corner higher-order states are specified by information entropy theory. This work not only gains insights into the active manipulation of topological phase transitions but also inspires novel strategies to design active topological materials through untethered methods, e.g., magnetism or biological cells.

Delocalization and higher-order topology in a nonlinear elastic lattice

“…Besides first-order elastic TIs [13][14][15][16][17][18], HOTIs have also been explored in elastic wave systems [8,[19][20][21][22][23][24] to manipulate mechanical energy transfer and information transmission [25,26]. Typical examples include the development of new technologies and device for vibration control [21,27,28], information processing [29], and analog computation [30], among others.…”

Theoretical and experimental demonstrations of the transversely symmetric and antisymmetric properties of topological edge states

“…In the field of phononic crystals (PCs) and metamaterials, the topological edge states (TES) that occur at the edges * Authors to whom any correspondence should be addressed. of topological insulators or at interfaces between PCs with opposite topological phases have attracted wide and intense interest for both acoustic and elastic waves [1][2][3][4][5][6][7][8][9][10][11][12][13]. TES provide an approach for transporting phonon [14][15][16][17] information in a helical way with significant features.…”