title: Topological mechanics of gyroscopic metamaterials.
abstract: Topological mechanical metamaterials are artificial structures whose unusual properties are protected very much like their electronic and optical counterparts. Here, we present an experimental and theoretical study of an active metamaterial--composed of coupled gyroscopes on a lattice--that breaks time-reversal symmetry. The vibrational spectrum displays a sonic gap populated by topologically protected edge modes that propagate in only one direction and are unaffected by disorder. We present a mathematical model that explains how the edge mode chirality can be switched via controlled distortions of the underlying lattice. This effect allows the direction of the edge current to be determined on demand. We demonstrate this functionality in experiment and envision applications of these edge modes to the design of one-way acoustic waveguides.
authors.affiliation: James Franck Institute and Department of Physics, The University of Chicago, Chicago, IL 60637;
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Nash
authors.affiliation: James Franck Institute and Department of Physics, The University of Chicago, Chicago, IL 60637;
authors.forename: Dustin
authors.initials: D
authors.lastname: Kleckner
authors.affiliation: James Franck Institute and Department of Physics, The University of Chicago, Chicago, IL 60637;
authors.forename: Alismari
authors.initials: A
authors.lastname: Read
authors.affiliation: Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, 2300 RA Leiden, The Netherlands;
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Vitelli
authors.affiliation: Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 aturne26@jhu.edu wtmirvine@uchicago.edu.
authors.forename: Ari M
authors.initials: AM
authors.lastname: Turner
authors.affiliation: James Franck Institute and Department of Physics, The University of Chicago, Chicago, IL 60637; aturne26@jhu.edu wtmirvine@uchicago.edu.
authors.forename: William T M
authors.initials: WT
authors.lastname: Irvine
keywords: gyroscopic metamaterial; metamaterial; topological mechanics