Roton

In theoretical physics, a roton is an elementary excitation, or quasiparticle, seen in superfluid helium-4 and Bose–Einstein condensates with long-range dipolar interactions or spin-orbit coupling. The dispersion relation of elementary excitations in this superfluid shows a linear increase from the origin, but exhibits first a maximum and then a minimum in energy as the momentum increases. Excitations with momenta in the linear region are called phonons; those with momenta close to the minimum are called rotons. Excitations with momenta near the maximum are called maxons.

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]

^ Wang, Ke; Chen, Yi; Kadic, Muamer; Wang, Changguo; Wegener, Martin (24 May 2022). "Nonlocal interaction engineering of 2D roton-like dispersion relations in acoustic and mechanical metamaterials". Communications Materials. 3 (1): 35. Bibcode:2022CoMat...3...35W. doi:10.1038/s43246-022-00257-z. S2CID 248991736.
^ Chen, Yi; Kadic, Muamer; Wegener, Martin (2 June 2021). "Roton-like acoustical dispersion relations in 3D metamaterials". Nature Communications. 12 (1): 3278. Bibcode:2021NatCo..12.3278C. doi:10.1038/s41467-021-23574-2. PMC 8172548. PMID 34078904.
^ Iglesias Martínez, Julio Andrés; Groß, Michael Fidelis; Chen, Yi; Frenzel, Tobias; Laude, Vincent; Kadic, Muamer; Wegener, Martin (2021-12-03). "Experimental observation of roton-like dispersion relations in metamaterials". Science Advances. 7 (49): eabm2189. Bibcode:2021SciA....7.2189I. doi:10.1126/sciadv.abm2189. ISSN 2375-2548. PMC 8635434. PMID 34851658.

[1] Wang, Ke; Chen, Yi; Kadic, Muamer; Wang, Changguo; Wegener, Martin (24 May 2022). "Nonlocal interaction engineering of 2D roton-like dispersion relations in acoustic and mechanical metamaterials". Communications Materials. 3 (1): 35. Bibcode:2022CoMat...3...35W. doi:10.1038/s43246-022-00257-z. S2CID 248991736.

[2] Chen, Yi; Kadic, Muamer; Wegener, Martin (2 June 2021). "Roton-like acoustical dispersion relations in 3D metamaterials". Nature Communications. 12 (1): 3278. Bibcode:2021NatCo..12.3278C. doi:10.1038/s41467-021-23574-2. PMC 8172548. PMID 34078904.

[3] Iglesias Martínez, Julio Andrés; Groß, Michael Fidelis; Chen, Yi; Frenzel, Tobias; Laude, Vincent; Kadic, Muamer; Wegener, Martin (2021-12-03). "Experimental observation of roton-like dispersion relations in metamaterials". Science Advances. 7 (49): eabm2189. Bibcode:2021SciA....7.2189I. doi:10.1126/sciadv.abm2189. ISSN 2375-2548. PMC 8635434. PMID 34851658.

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