We have obtained new information on the elementary excitations in superfluid He-4 by studying local observables relative to roton wave-packets built from accurate variational representations of the excited states. The same technique has been applied also to study a pure 2-Dimensional system, where the spectrum, computed through a variational Monte Carlo simulation, still shows a modified phonon-maxon-roton dispersion relation. In the roton region, collective quantum effects are present, but when the average momentum of the wave-packet matches with the wave-vector of the roton minimum the interference effects between neighboring atoms disappear and the local density and momentum essentially coincide with those of a single particle excitation. A roton, as well as a single particle excitation, has a velocity vector field which is very similar to that of a smoke-ring scaled down to atomic size.

Roton wave-packets in 3-dimensional and 2-dimensional He-4 / D. E. Galli, L. Reatto. - In: JOURNAL OF LOW TEMPERATURE PHYSICS. - ISSN 0022-2291. - 110:1-2(1998), pp. 437-442.

Roton wave-packets in 3-dimensional and 2-dimensional He-4

D. E. Galli
Primo
;
L. Reatto
1998

Abstract

We have obtained new information on the elementary excitations in superfluid He-4 by studying local observables relative to roton wave-packets built from accurate variational representations of the excited states. The same technique has been applied also to study a pure 2-Dimensional system, where the spectrum, computed through a variational Monte Carlo simulation, still shows a modified phonon-maxon-roton dispersion relation. In the roton region, collective quantum effects are present, but when the average momentum of the wave-packet matches with the wave-vector of the roton minimum the interference effects between neighboring atoms disappear and the local density and momentum essentially coincide with those of a single particle excitation. A roton, as well as a single particle excitation, has a velocity vector field which is very similar to that of a smoke-ring scaled down to atomic size.
Settore FIS/03 - Fisica della Materia
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/190295
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