Reconfigurable higher-order topological electromechanical metamaterial

Abstract

Higher-order topological insulators (HOTIs) exhibit hierarchical and multidimensional features of topological states, expanding the applications of topological insulators (TIs). Reconfigurable mechanical metamaterial-based HOTIs for the manipulation of elastic waves are highly desirable. Here, we propose a reconfigurable electromechanical metamaterial with first-order topological edge states and second-order topological corner states for the control of Lamb waves. The metamaterial consists of an aluminum layer sandwiched between two piezoelectric layers shunted through negative capacitance circuits. The topology of the metamaterial can be reconfigured by switching on or off the connected circuits, and the metamaterial is also tunable by changing the electrical parameters. Hierarchical and multidimensional topological waveguides are constructed and their reconfigurability is demonstrated. The metamaterial is continuous and thus facilitates waveguide miniaturization, such as on-chip device design.