2D-phononic system with local phase transition and reconfigurable non-contact modulation

Abstract Contactless tuning of signals represents a promising avenue for advancing topological phononics and photonics devices, particularly in the frequency and spatial domains. For topological phase transitions, breaking the spatial inversion symmetry geometrically to obtain an open topological band gap is a typical way to introduce perturbations. This approach has great limitations in achieving reconfigurable topological protection routes. We present a thermally modulated two-dimensional elastic topological insulator made from a patterned substrate and a temperature-sensitive vanadium dioxide film, allowing elastic waves to propagate in the suspended region of the 2D material. The topological phase transition is activated by locally heating a portion of the unit cell. This heating induces a phase transition in the material by exploiting changes in mechanical properties, achieving symmetry breaking. The topological valley-locked states with strong localization at the interface are obtained by placing unit cells with different chirality adjacent to each other at the omnidirectional bulk band gap. Full-field simulations confirm both the reconfigurability of arbitrary paths and the robustness of the induced waves against defects. Eliminating the need for pre-etched topological protection paths on patterned substrates enhances flexibility in both manufacturing and application. This innovative scheme employs localized temperature control at the unit cell scale to achieve effects akin to approximately 10% geometric symmetry breaking, thereby significantly reducing precision manufacturing requirements. Moreover, localized thermal modulation holds considerable potential for improving modulation rates while minimizing energy loss.