Edge states and topological metamaterials
Topological metamaterials
The field of condensed matter physics has soared to new heights with the recent discovery of topological quantum matter. Topological insulating and superconducting materials, with the ability to support robust and defect-immune manipulation of electrons, have emerged as enabling candidates for the second quantum revolution. Numerous topological phenomena have also found their way from the quantum realm to the classical despite the fundamental differences between electrons (fermions) and photons or phonons (bosons), and opened the way for new technologies relevant to optical, phononic, mechanical computing, and autonomous materials. Here, we investigate mechanical systems supporting topological edge states via analogs of the Kitaev model, Su-Schrieffer-Heeger (SSH) model and mass-dimer model, for example.
Articles related to topological metamaterials:
5 - Allein, F., Chaunsali, R., Anastasiadis, A., Frankel, I., Boechler, N., Diakonos, F. K., & Theocharis, G.,
Duality of topological edge states in a mechanical Kitaev chain.
4 - Miniaci, M., Allein, F., & Pal, R. K.,
Spectral flow of localized mode in elastic media.
Phys. Rev. Applied 20, 064018 (2023). PDF
3 - Allein, F., Anastasiadis, A., Chaunsali, R., Frankel, I., Boechler, N., Diakonos, F. K., & Theocharis, G.,
Strain topological metamaterials and revealing hidden topology in higher-order coordinates.
Nature Communications 14:6633 (2023). PDF
Edge states in mechanical granular systems:
As a new class of artificial elastic materials, granular crystals are mechanical structures of elastic beads arranged in contact through a lattice. One important feature of wave dynamics in granular crystals is that it highly relies on the contact mechanics, allowing for exotic wave transport properties such as rotational waves, solitary waves, slow edge waves, topological edge waves, etc. Realizing granular structures with well-predicted wave physics not only renders these new properties to mechanical systems, but provides also significant possibilities for advanced elastic wave control scenarios.
Here, we theoretically and experimentally study the linear wave dynamics in one-dimensional (1D) zigzag granular chains and two-dimensional granular graphene constructed with macroscopic spherical stainless steel/tungsten beads. A spring–mass model including normal, shear and bending mechanical couplings between beads is proposed to characterize the wave dynamics in the chain, which turns out to exhibit remarkable agreement with the experimental measurements. Our work confirms the existence of localized translational–rotational coupled modes at the ends of granular chains, and it might motivate future studies for novel topological wave effects in granular structures. In addition, granular graphene can serve as an excellent experimental platform to study Dirac, topological, and nonlinear wave phenomena.
Articles related to edge states in mechanical granular systems:
2 - Zheng, L.-Y., Allein, F, Tournat, V., Gusev, V., and Theocharis G.,
Granular graphene: Direct observation of edge states on zigzag and armchair boundaries,
Phys. Rev B 99, 184113 (2019). PDF
1 - Zheng, L.-Y., Qu, S.,Allein, F, Thréard, T., Gusev, V., Tournat, V. and Theocharis G.,
Direct observation of edge modes in zigzag granular chains,
Journal of Sound and Vibration 526, 116761 (2022). PDF
