title: Coupled membranes with doubly negative mass density and bulk modulus.
abstract: We present a structurally and conceptually simple acoustic double negative metamaterial comprising two coupled membranes. Owing to its symmetry, the system can generate both monopolar and dipolar resonances that are separately tunable, thereby making broadband double negativity possible. A homogenization scheme is implemented that enables the exact characterization of our metamaterial by the effective mass density and bulk modulus even beyond the usual long-wavelength regime, with the measured displacement fields on the sample's surfaces as inputs. Double negativity is achieved in the frequency range of 520-830 Hz. Transmission and reflection predictions using effective parameters are shown to agree remarkably well with the experiment.
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Guancong
authors.initials: G
authors.lastname: Ma
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Yang
authors.forename: Ping
authors.initials: P
authors.lastname: Sheng