Space-coiling metamaterials with double negativity and conical dispersion

Area of Science:

• Physics
• Materials Science
• Acoustics
• Electromagnetism

Background:

• Metamaterials exhibit extraordinary dispersion, with examples including negative index, zero index, and extremely anisotropic metamaterials.
• Conventional metamaterials often rely on locally resonating elements, which can lead to undesirable absorption.
• There is a significant need for alternative methods to achieve unusual metamaterial properties without inherent absorption losses.

Purpose of the Study:

• To demonstrate an alternative approach for constructing metamaterials with extreme dispersion using a geometric method.
• To create acoustic metamaterials exhibiting conical dispersion and negative refraction with airborne sound.
• To design and realize a double-negative metamaterial for microwaves based on the same principle.

Main Methods:

• Utilizing a geometric approach by coiling up space with curled channels to engineer metamaterial properties.
• Developing an acoustic metamaterial with conical dispersion for airborne sound applications.
• Designing and fabricating a double-negative metamaterial for microwave frequencies.

Main Results:

• Successfully constructed metamaterials with extreme dispersion via curled channels, avoiding resonant elements.
• Achieved the first demonstration of negative refraction from an acoustic metamaterial using airborne sound.
• Realized a double-negative metamaterial for microwaves employing the same spatial coiling principle.

Conclusions:

• The geometric approach of coiling space offers a viable alternative route to achieve extreme dispersion in metamaterials.
• This method allows for tunable properties, such as the ratio of wavelength to lattice constant for negative or zero index.
• The demonstrated acoustic and microwave metamaterials highlight the versatility and effectiveness of the spatial coiling technique.