Experimental observation of roton-like dispersion relations in metamaterials

Abstract

Previously, rotons were observed in correlated quantum systems at low temperatures, including superfluid helium and Bose-Einstein condensates. Here, following a recent theoretical proposal, we report the direct experimental observation of roton-like dispersion relations in two different three-dimensional metamaterials under ambient conditions. One experiment uses transverse elastic waves in microscale metamaterials at ultrasound frequencies. The other experiment uses longitudinal air-pressure waves in macroscopic channel-based metamaterials at audible frequencies. In both experiments, we identify the roton-like minimum in the dispersion relation that is associated to a triplet of waves at a given frequency. Our work shows that designed interactions in metamaterials beyond the nearest neighbors open unprecedented experimental opportunities to tailor the lowest dispersion branchwhile most previous metamaterial studies have concentrated on shaping higher dispersion branches.

Brillouin Light Scattering Characterisation of Gray Tone 3D Printed Isotropic Materials

“…For IP-S, this aspect is more pronounced and we reach a plateau very fast. It is often observed in the literature that faster polymerisation combined with better diffusion results in more homogeneous sample properties and thus in a better surface and volume quality [14]. Here, we furthermore emphasize the importance of damping that increases for both photoresins when the laser power decreases.…”

“…A few extensive studies have been performed on different polymers to obtain the printable properties as a function of printing parameters, via Raman scattering or other characterisation techniques [14,15]. However, from one setup to another and for different reasons, characterisation must be repeated and adapted each time.…”

Coupled acoustic resonance for wave control and sensing

“…This negative slope (wavenumber B) implies that the energy flow is reversed, while the phase velocity (v ph = ω/k z ) remains positive. The theoretical finding was validated with experimental observation [72,73]. Such Roton-like characteristics observed in correlated quantum superfuids are realized in the classical system relying on coupled resonators, which can serve as simple tabletop experiments for condensed matter physics and quantum mechanics [75].…”

Engineering nonreciprocal wave dispersion in a nonlocal micropolar metabeam

“…One of the prominent features is multiple eigenmodes supported at a single frequency, featuring net negative energy flows which are analogous to the so-called “return flow.” Up to now, there have been mainly two approaches to achieving the roton-like mechanical and acoustic bands: chiral 26 and nonlocal interactions. 27,28 Here, we emphasize that with the nonlocal metabeam design, both reciprocal and nonreciprocal roton-like dispersion relations can be observed with the help of extra nonlocal degree of freedom.…”