Negative effective mass below a cut-off frequency

TL;DR

This paper explores negative effective mass phenomena below a cut-off frequency through theoretical and experimental studies on mass-spring structures, waveguides, and elastic metamaterials, revealing new insights into wave propagation control.

Contribution

It introduces the first combined theoretical and experimental analysis of negative effective mass below a cut-off frequency in various elastic systems and designs novel metamaterials exhibiting this behavior.

Findings

Negative effective mass observed below a specific frequency in mass-spring systems.

Transmission drop caused by negative effective mass demonstrated experimentally.

Designed elastic metamaterials exhibit negative effective mass below a cut-off frequency.

Abstract

Negative mass phenomena occurring below a cut-off frequency is examined by both theoretical and experimental methods. The paper begins with the investigation on a mass-spring structure, the effective mass of which is shown to be negative below a specific frequency. Due to the decaying nature of lattice waves in the negative-mass system, the transmission drop induced by negative effective mass is demonstrated experimentally. Further investigation is conducted for a rectangular solid waveguide with clamped boundary conditions. It is shown that the lowest bandgap mode of the clamped waveguide can be attributed to negative effective mass below a cut-off frequency. Based on this observation, elastic metamaterials made of the steel grid filled by styrene butadiene rubber are designed and fabricated. Both simulation and experimental analyses demonstrate that the designed metamaterial have negative effective mass below a cut-off frequency.