title: Transformable topological mechanical metamaterials.
abstract: Mechanical metamaterials are engineered materials whose structures give them novel mechanical properties, including negative Poisson's ratios, negative compressibilities and phononic bandgaps. Of particular interest are systems near the point of mechanical instability, which recently have been shown to distribute force and motion in robust ways determined by a nontrivial topological state. Here we discuss the classification of and propose a design principle for mechanical metamaterials that can be easily and reversibly transformed between states with dramatically different mechanical and acoustic properties via a soft strain. Remarkably, despite the low energetic cost of this transition, quantities such as the edge stiffness and speed of sound can change by orders of magnitude. We show that the existence and form of a soft deformation directly determines floppy edge modes and phonon dispersion. Finally, we generalize the soft strain to generate domain structures that allow further tuning of the material.
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.|Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501, USA.|School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: D Zeb
authors.initials: DZ
authors.lastname: Rocklin
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
authors.forename: Shangnan
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
authors.forename: Kai
authors.identifier: 0000-0001-9595-7646
authors.initials: K
authors.lastname: Sun
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Mao