title: Polarization bandgaps and fluid-like elasticity in fully solid elastic metamaterials.
abstract: Elastic waves exhibit rich polarization characteristics absent in acoustic and electromagnetic waves. By designing a solid elastic metamaterial based on three-dimensional anisotropic locally resonant units, here we experimentally demonstrate polarization bandgaps together with exotic properties such as 'fluid-like' elasticity. We construct elastic rods with unusual vibrational properties, which we denote as 'meta-rods'. By measuring the vibrational responses under flexural, longitudinal and torsional excitations, we find that each vibration mode can be selectively suppressed. In particular, we observe in a finite frequency regime that all flexural vibrations are forbidden, whereas longitudinal vibration is allowed-a unique property of fluids. In another case, the torsional vibration can be suppressed significantly. The experimental results are well interpreted by band structure analysis, as well as effective media with indefinite mass density and negative moment of inertia. Our work opens an approach to efficiently separate and control elastic waves of different polarizations in fully solid structures.
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.|Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Guancong
authors.initials: G
authors.lastname: Ma
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Caixing
authors.initials: C
authors.lastname: Fu
authors.affiliation: College of Physics, Optoelectronics and Energy &Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China.
authors.forename: Guanghao
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Philipp
authors.initials: P
authors.lastname: Del Hougne
authors.affiliation: Instituto Gregorio Millán Barbany, Universidad Carlos III de Madrid, Avenida de la Universidad 30 Leganés, Madrid 28916, Spain.
authors.forename: Johan
authors.initials: J
authors.lastname: Christensen
authors.affiliation: College of Physics, Optoelectronics and Energy &Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Lai
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.|Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Ping
authors.initials: P
authors.lastname: Sheng