Roton dispersion relation, showing the quasiparticle energy E(p) as a function of momentum p. A quasiparticle with momentum generated in the local energy minimum is called a roton.
The term "roton-like" is also used for the predicted eigenmodes in 3D metamaterials using beyond-nearest-neighbor coupling.[1][2] The observation of such a "roton-like" dispersion relation was demonstrated under ambient conditions for both acoustic pressure waves in a channel-based metamaterial at audible frequencies and transverse elastic waves in a microscale metamaterial at ultrasound frequencies.[3]