Direct Evidence for R
            <sup>−</sup>
            Rotons Having Antiparallel Momentum and Velocity

Tucker, M. A. H.; Wyatt, A. F. G.

doi:10.1126/science.283.5405.1150

Cited by 102 publications

(60 citation statements)

References 13 publications

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“…This type of confirmation of the anomalous connection between velocity and momentum of the R − rotons [20] [21] is accomplished in the experiment pictured in Fig. 7.…”

Section: Direct Detection Of R − Rotonsmentioning

confidence: 90%

Semiclassical mechanics of rotons

Sanders¹

2001

Contemporary Physics

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The elementary excitations in superfluid liquid 4 He named rotons have an unusual dispersion curve. The energy is an approximately quadratic function of (p − p 0 ), the difference between the magnitude of the momentum p and a characteristic value p 0 . As a result, while for p > p 0 a roton has its (group) velocity parallel to its momentum, when p < p 0 the velocity and momentum are antiparallel. When p = p 0 , the roton has non-zero momentum but zero velocity. These kinematic properties lead to unusual trajectories when rotons scatter or experience external forces. This paper examines this behavior in the classical (ray optics) limit, where the roton wavelength is small compared with all other dimensions. Several experiments illustrate these effects. The examples are interesting in themselves, and also offer unconventional pedagogical possibilities.

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“…This type of confirmation of the anomalous connection between velocity and momentum of the R − rotons [20] [21] is accomplished in the experiment pictured in Fig. 7.…”

Section: Direct Detection Of R − Rotonsmentioning

confidence: 90%

Semiclassical mechanics of rotons

Sanders¹

2001

Contemporary Physics

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“…In superfluid helium there exist quasiparticles with different energy-momentum relations, phonons with an almost linear relation, R + -rotons with a relation which is close to quadratic but at a finite energy and momentum, and R --rotons, whose velocity and momentum have opposite directions. The results of experiments on phonon pulses can be found in [1,2], R + -rotons in [3,4], and R --rotons in [5].…”

Section: Introductionmentioning

confidence: 91%

Evolution of a pulse of noninteracting quasiparticles with dispersion and initial angular width

Adamenko

Nemchenko

Slipko

et al. 2004

Low Temperature Physics

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The evolution of a pulse of noninteracting quasiparticles, caused by their different velocities and angular distribution of momenta, is studied theoretically. Equations are found that describe the shape of the pulse surface at any time. The time of the beginning, end and duration of the density of the quasiparticle energy flux is determined at a general spatial point. The quasiparticle energy density is considered at all times and positions, and it is shown that the region of high energy density, in the middle of the pulse, is equal to the initial energy density under certain conditions. These theoretical results are discussed in relation to experimental data on the evolution of a pulse of noninteracting phonons in superfluid helium.

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“…So, for example, in the experiments of [1,2] the quasiparticles of superfluid helium were created on the interface with a heated solid. Then the propagation of quasiparticles in superfluid helium and their reflection from various interfaces was investigated.…”

Section: Introductionmentioning

confidence: 99%

Normal transmission of phonons with anomalous dispersion through the interface of two continuous media

Adamenko

Nemchenko

Tanatarov

2006

Low Temperature Physics

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In this work the problem is solved of normal transmission of quasiparticles through the interface of two continuous media, one of which is quantum fluid. The quantum fluid is described as a continuous medium with correlations. Within the framework of this approach the dispersion relation of the quantum fluid 9( ) k can be arbitrary. The integral equation describing it in a half-space is solved by the Wiener-Hopf method, and its general solution is obtained. This approach is applied to the dispersion relation of the Bose-Einstein condensate. It is shown that the solutions of equations of quantum fluid in a half-space are traveling waves deformed near the border by specific surface standing waves. By means of boundary conditions the general solution in the whole space is obtained. Expressions for transmission and reflection factors of waves in both directions are derived, depending on their frequency. The results are important for describing the creation of helium II phonons on the boundary with a solid, and are of interest for classical acoustics.

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Direct Evidence for R ⁻ Rotons Having Antiparallel Momentum and Velocity

Cited by 102 publications

References 13 publications

Semiclassical mechanics of rotons

Semiclassical mechanics of rotons

Evolution of a pulse of noninteracting quasiparticles with dispersion and initial angular width

Normal transmission of phonons with anomalous dispersion through the interface of two continuous media

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Direct Evidence for R − Rotons Having Antiparallel Momentum and Velocity

Cited by 102 publications

References 13 publications

Semiclassical mechanics of rotons

Semiclassical mechanics of rotons

Evolution of a pulse of noninteracting quasiparticles with dispersion and initial angular width

Normal transmission of phonons with anomalous dispersion through the interface of two continuous media

Contact Info

Product

Resources

About

Direct Evidence for R ⁻ Rotons Having Antiparallel Momentum and Velocity