Rotons and Roton Wave Packets in Superfluid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi>He</mml:mi></mml:math>

Galli, D. E.; Cecchetti, E.; Reatto, L.

doi:10.1103/physrevlett.77.5401

Cited by 34 publications

(20 citation statements)

References 12 publications

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“…A visualization of such roton backflow can be found in Ref. 12 where roton wave packets have been studied by a microscopic theory. As far as we know, no study of a vortex in the 3D 4 He based on advanced QMC methods has been performed yet and this is the problem that we address in the present study of a straight vortex line in condensed 4 He via the shadow path integral ground state 28,29 (SPIGS) method with fixed phase approximation.…”

Section: -14mentioning

confidence: 99%

Quantum Monte Carlo study of a vortex in superfluidHe4and search for a vortex state in the solid

Galli

Reatto²,

Rossi

2014

Phys. Rev. B

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We have performed a microscopic study of a straight quantized vortex line in three dimensions in condensed 4 He at zero temperature using the Shadow Path Integral Ground State method and the fixed-phase approximation. We have characterized the energy and the local density profile around the vortex axis in superfluid 4 He at several densities, ranging from below the equilibrium density up to the overpressurized regime. For the Onsager-Feynman (OF) phase our results are exact and represent a benchmark for other theories. The inclusion of backflow correlations in the phase improves the description of the vortex with respect to the OF phase by a large reduction of the core energy of the topological excitation. At all densities the phase with backflow induces a partial filling of the vortex core and this filling slightly increases with density. The core size slightly decreases for increasing density and the density profile has well defined density dependent oscillations whose wave vector is closer to the wave vector of the main peak in the static density response function rather than to the roton wave vector. Our results can be applied to vortex rings of large radius R and we find good agreement with the experimental value of the energy as function of R without any free parameter. We have studied also 4 He above the melting density in the solid phase using the same functional form for the phase as in the liquid. We found that off-diagonal properties of the solid are not qualitatively affected by the velocity field induced by the vortex phase, both with and without backflow correlations. Therefore we find evidence that a perfect 4 He crystal is not a marginally stable quantum solid in which rotation would be able to induce off-diagonal long-range coherence.

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Section: -14mentioning

confidence: 99%

Quantum Monte Carlo study of a vortex in superfluidHe4and search for a vortex state in the solid

Galli

Reatto²,

Rossi

2014

Phys. Rev. B

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“…10 Furthermore, the SWF technique extended to excited states has been shown to be able to treat very accurately backflow effects. 11 A SWF for N bosons can be written as the integral over a set of N auxiliary vector variables ͑shadow variables͒ Sϭ͕s ជ 1 , . .…”

Section: Shadow Wave Functionmentioning

confidence: 99%

Alkali ions in superfluid4Heand structure of the snowball

2001

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We performed variational Monte Carlo simulations of an alkali ion impurity (Li ϩ , Na ϩ , K ϩ , and Cs ϩ ) in liquid 4 He at the equilibrium density and Tϭ0 K using the shadow wave function technique. We calculated the chemical potential, the local order, the single-particle excitation spectrum, and the effective mass of the ions. In all cases the first shell of He atoms is ordered, forming what is usually called a snowball. The radial density profiles and angular correlations show that the microscopic structure of the snowball is remarkably different for each ion. Only in the case of Na ϩ and K ϩ are the atoms of the first shell essentially localized so that the snowball can be considered as a solid. In the case of Li ϩ and Cs ϩ these He atoms readily exchange with the others and this difference shows up dramatically in the values of the effective masses. The local order is simple cubic in the case of Li ϩ and face-centered cubic in the case of K ϩ .

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“…x + q 2 y , and as wave function of the bulk excited states we adopt for ψ q the shadow variational wave function [35][36][37][38] and explore different packets, as discussed in the SM. Density can be computed by means of a Monte Carlo sampling and search for parameters of the packets giving density profiles close to that of the vortex.…”

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confidence: 99%

Probing Quantum Turbulence in He4 by Quantum Evaporation Measurements

2018

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Theory of superfluid ^{4}He shows that, due to strong correlations and backflow effects, the density profile of a vortex line has the character of a density modulation and it is not a simple rarefaction region as found in clouds of cold bosonic atoms. We find that the basic features of this density modulation are represented by a wave packet of cylindrical symmetry in which rotons with a positive group velocity have a dominant role: The vortex density modulation can be viewed as a cloud of virtual excitations, mainly rotons, sustained by the phase of the vortex wave function. This suggests that in a vortex reconnection some of these rotons become real so that a vortex tangle is predicted to be a source of nonthermal rotons. The presence of such vorticity induced rotons can be verified by measurements at low temperature of quantum evaporation of ^{4}He atoms. We estimate the rate of evaporation and this turns out to be detectable by current instrumentation. Additional information on the microscopic processes in the decay of quantum turbulence will be obtained if quantum evaporation by high energy phonons should be detected.

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Rotons and Roton Wave Packets in Superfluid4He

Cited by 34 publications

References 12 publications

Quantum Monte Carlo study of a vortex in superfluidHe4and search for a vortex state in the solid

Quantum Monte Carlo study of a vortex in superfluidHe4and search for a vortex state in the solid

Alkali ions in superfluid4Heand structure of the snowball

Probing Quantum Turbulence in He4 by Quantum Evaporation Measurements

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