Topologically protected elastic waves in phononic metamaterials

Topologically protected elastic waves in phononic metamaterials

Surface waves in topological states of quantum matter exhibit unique protection from backscattering induced by disorders, making them ideal carriers for both classical and quantum information. Topological matters for electrons and photons are largely limited by the range of bulk properties, and the associated performance trade-offs. In contrast, phononic metamaterials provide access to a much w...

Topologically protected states in active photonic metamaterials

Background: A topologist is sometimes described as a mathematician who cannot discriminate between a tea cup and a doughnut. This means that topology focuses on global properties such as connectedness instead of geometrical detail, thereby paving the road for a new level of understanding. Topological invariants such as the Euler characteristic for surfaces in R are naturally quantized and do no...

Experimental evidence of rotational elastic waves in granular phononic crystals.

A generalized theory of elasticity, taking into account the rotational degrees of freedom of point bodies constituting a continuum, was proposed at the beginning of the twentieth century by the Cosserat brothers. We report the experimental observation of coupled rotational-translational modes in a noncohesive granular phononic crystal. While absent in the classical theory of elasticity, these e...

Topological Phononic Crystals with One-Way Elastic Edge Waves.

We report a new type of phononic crystals with topologically nontrivial band gaps for both longitudinal and transverse polarizations, resulting in protected one-way elastic edge waves. In our design, gyroscopic inertial effects are used to break the time-reversal symmetry and realize the phononic analogue of the electronic quantum (anomalous) Hall effect. We investigate the response of both hex...

Focusing guided waves using surface bonded elastic metamaterials