Search

Waveguides for mechanical signal transmission in the megahertz to gigahertz regimes enable on-chip phononic circuitry, which brings new capabilities complementing photonics and electronics. Lattices of coupled nano-electromechanical drumhead resonators are suitable for these waveguides due to their high Q-factor and precisely engineered band structure. Here, we show that thermally induced elastic buckling of such resonators causes a phase transition in the waveguide leading to reversible control of signal transmission. Specifically, when cooled, the lowest-frequency transmission band associated with the primary acoustic mode vanishes. Experiments show the merging of the lower and upper band gaps, such that signals remain localized at the excitation boundary. Numerical simulations show that the temperature-induced destruction of the pass band is a result of inhomogeneous elastic buckling, which disturbs the waveguide's periodicity and suppresses the wave propagation. Mechanical phase transitions in waveguides open opportunities for drastic phononic band reconfiguration in on-chip circuitry and computing.

Two-dimensional (2D) van der Waals materials are both highly deformable atomic membranes and electrically active quantum materials. Most electronic and quantum states in both monolayer 2D materials and heterostructures are highly sensitive to strain and interlayer structure, and thus may be tuned mechanically. Here we explore the current frontiers using 2D material mechanics to sense, tune, tailor or even reconfigure electronic properties, device behavior and quantum states. We compare the relative impacts of different kinds of mechanical perturbations including in-plane strain, out-of-plane vibrations, inhomogeneous three-dimensional deformations, instabilities of membranes under compression like crumpling and wrinkling, and interlayer slip. Throughout, we explore how each form of coupling may be used for applications that cannot be realized in the flat unperturbed materials including tunable nanoelectromechanical systems, strain resilient electronics, multifunctional surfaces and reconfigurable quantum systems.