2,489 research outputs found
Superlensing effect of an anisotropic metamaterial slab with near-zero dynamic mass
A metamaterial slab of anisotropic mass with one diagonal component being
infinity and the other being zero is demonstrated to behave as a superlens for
acoustic imaging beyond the diffraction limit. The underlying mechanism for
extraordinary transmission of evanescent waves is attributed to the zero mass
effect. Microstructure design for such anisotropic lens is also presented. In
contrast to the anisotropic superlens based on Fabry-P\'erot resonant
mechanism, the proposed lens operates without the limitation on lens thickness,
thus more flexible in practical applications. Numerical modeling is performed
to validate the proposed ideas.Comment: 4 figure
Topological mechanics in quasicrystals
We study topological mechanics in two-dimensional quasicrystalline
parallelogram tilings. Topological mechanics has been studied intensively in
periodic lattices in the past a few years, leading to the discovery of
topologically protected boundary floppy modes in Maxwell lattices. In this
paper we extend this concept to quasicrystalline parallelogram tillings and we
use the Penrose tiling as our example to demonstrate how these topological
boundary floppy modes arise with a small geometric perturbation to the tiling.
The same construction can also be applied to disordered parallelogram tilings
to generate topological boundary floppy modes. We prove the existence of these
topological boundary floppy modes using a duality theorem which relates floppy
modes and states of self stress in parallelogram tilings and fiber networks,
which are Maxwell reciprocal diagrams to one another. We find that, due to the
unusual rotational symmetry of quasicrystals, the resulting topological
polarization can exhibit orientations not allowed in periodic lattices. Our
result reveals new physics about the interplay between topological states and
quasicrystalline order, and leads to novel designs of quasicrystalline
topological mechanical metamaterials.Comment: 16 pages, 8 figure
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