Characterization of two-dimensional cellular elastic topological insulators based on regular-hexagon carriers

Abstract

An elastic topological insulator with pseudo-spin characteristics is designed based on honeycomb lattice phononic crystals with positive hexagonal carriers, which can realize path defect immunity and backscattering suppression transmission characteristics. By introducing a positive hexagon carrier with a certain size at the narrow diameter junction of the two-dimensional honeycomb structure to achieve symmetry breaking, a four-fold accidental degeneracy point can be obtained by adjusting the cell parameters. The main variable of the primitive cell is the hexagonal carrier side length [Formula: see text]. It is found that the four-fold Dirac point can be opened and a band gap can be formed by contracting the positive hexagonal carrier. Inversion of the energy band occurred in the separated two-fold degenerate state, for which the transformation of mediocre state and nonmediocre state had been realized so that the structure with acoustic pseudo-spin and topological edge state could be obtained. Based on the principle of body-edge state correspondence, the topologically protected edge acoustic transmission is simulated by the construction of the edge states combined with the connection of different structural systems. Further, different elastic phonon crystal structures are constructed, and the characteristics of path defect immunity and back-scattering suppression of elastic wave propagation by topological edge states are verified. The designed elastic topological insulators have great application prospects in the regulation of elastic waves.