Observation of phononic helical edge states in a mechanical 'topological insulator'
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TLDR
The collective behavior of mechanical oscillators exhibiting the phenomenology of the quantum spin Hall effect is characterized, and the phononic edge modes are shown to be helical, and this may enable the design of topological acoustic metamaterials that can capitalize on the stability of the surface phonons as reliable wave guides.Abstract:
A topological insulator is characterized by a dichotomy between the interior and the edge of a finite system: While the bulk has a non-zero energy gap, the edges are forced to sustain excitations traversing these gaps. Originally proposed for electrons governed by quantum mechanics, it has remained an important open question if the same physics can be observed for systems obeying Newton's equations of motion. Here, we report on measurements that characterize the collective behavior of mechanical oscillators exhibiting the phenomenology of the quantum spin hall effect. The phononic edge modes are shown to be helical and we demonstrate their topological protection via the stability against imperfections. Our results open the door to the design of topological acoustic meta-materials that can capitalize on the stability of the surfaces phonons as reliable wave guides.read more
Citations
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References
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Journal ArticleDOI
Colloquium: Topological insulators
M. Z. Hasan,Charles L. Kane +1 more
TL;DR: In this paper, the theoretical foundation for topological insulators and superconductors is reviewed and recent experiments are described in which the signatures of topologically insulators have been observed.
Journal ArticleDOI
Topological insulators and superconductors
Xiao-Liang Qi,Shou-Cheng Zhang +1 more
TL;DR: Topological superconductors are new states of quantum matter which cannot be adiabatically connected to conventional insulators and semiconductors and are characterized by a full insulating gap in the bulk and gapless edge or surface states which are protected by time reversal symmetry.
Journal ArticleDOI
Quantum spin Hall effect in graphene
Charles L. Kane,Eugene J. Mele +1 more
TL;DR: Graphene is converted from an ideal two-dimensional semimetallic state to a quantum spin Hall insulator and the spin and charge conductances in these edge states are calculated and the effects of temperature, chemical potential, Rashba coupling, disorder, and symmetry breaking fields are discussed.
Journal ArticleDOI
Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
TL;DR: In this article, the quantum spin Hall (QSH) effect can be realized in mercury-cadmium telluride semiconductor quantum wells, a state of matter with topological properties distinct from those of conventional insulators.
Journal ArticleDOI
Z-2 Topological Order and the Quantum Spin Hall Effect
Charles L. Kane,Eugene J. Mele +1 more
TL;DR: The Z2 order of the QSH phase is established in the two band model of graphene and a generalization of the formalism applicable to multiband and interacting systems is proposed.