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Excitation spectrum in two-dimensional superfluid ⁴He

Excitation spectrum in two-dimensional superfluid ⁴He

In this work we perform an ab-initio study of an ideal two-dimensional sample of ⁴He atoms, a model for ⁴He films adsorbed on several kinds of substrates. Starting from a realistic hamiltonian we face the microscopic study of the excitation phonon–roton spectrum of the system at zero temperature...

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Main Authors: Arrigoni, F., Vitali, E., Galli, D.E., Reatto, L.
Format: Article
Language:English
Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2013
Series:Физика низких температур
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Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
Online Access:http://dspace.nbuv.gov.ua/handle/123456789/118751
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spelling irk-123456789-1187512017-06-01T03:06:10Z Excitation spectrum in two-dimensional superfluid ⁴He Arrigoni, F. Vitali, E. Galli, D.E. Reatto, L. Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии In this work we perform an ab-initio study of an ideal two-dimensional sample of ⁴He atoms, a model for ⁴He films adsorbed on several kinds of substrates. Starting from a realistic hamiltonian we face the microscopic study of the excitation phonon–roton spectrum of the system at zero temperature. Our approach relies on path integral ground state Monte Carlo projection methods, allowing to evaluate exactly the dynamical density correlation functions in imaginary time, and this gives access to the dynamical structure factor of the system S(q, ), containing information about the excitation spectrum E(q), resulting in sharp peaks in S(q, ). The actual evaluation of S(q, ) requires the inversion of the Laplace transform in ill-posed conditions, which we face via the genetic inversion via falsification of theories technique. We explore the full density range from the region of spinodal decomposition to the freezing density, i.e., 0.0321 Å⁻² – 0.0658 Å⁻². In particular we follow the density dependence of the excitation spectrum, focusing on the low-wave vector behavior of E(q), the roton dispersion, the strength of single quasiparticle peak, Z(q), and the static density response function, (q). As the density increases, the dispersion E(q) at low-wave vector changes from a superlinear (anomalous dispersion) trend to a sublinear (normal dispersion) one, anticipating the crystallization of the system; at the same time the maxon–roton structure, which is barely visible at low density, becomes well developed at high densities and the roton wave vector has a strong density dependence. Connection is made with recent inelastic neutron scattering results from highly ordered silica nanopores partially filled with ⁴He. 2013 Article Excitation spectrum in two-dimensional superfluid ⁴He / F. Arrigoni, E. Vitali, D.E. Galli, L. Reatto// Физика низких температур. — 2013. — Т. 39, № 9. — С. 1021–1030. — Бібліогр.: 37 назв. — англ. 0132-6414 PACS: 67.25.bh,67.25.dt http://dspace.nbuv.gov.ua/handle/123456789/118751 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
spellingShingle Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
Arrigoni, F.
Vitali, E.
Galli, D.E.
Reatto, L.
Excitation spectrum in two-dimensional superfluid ⁴He
Физика низких температур
description In this work we perform an ab-initio study of an ideal two-dimensional sample of ⁴He atoms, a model for ⁴He films adsorbed on several kinds of substrates. Starting from a realistic hamiltonian we face the microscopic study of the excitation phonon–roton spectrum of the system at zero temperature. Our approach relies on path integral ground state Monte Carlo projection methods, allowing to evaluate exactly the dynamical density correlation functions in imaginary time, and this gives access to the dynamical structure factor of the system S(q, ), containing information about the excitation spectrum E(q), resulting in sharp peaks in S(q, ). The actual evaluation of S(q, ) requires the inversion of the Laplace transform in ill-posed conditions, which we face via the genetic inversion via falsification of theories technique. We explore the full density range from the region of spinodal decomposition to the freezing density, i.e., 0.0321 Å⁻² – 0.0658 Å⁻². In particular we follow the density dependence of the excitation spectrum, focusing on the low-wave vector behavior of E(q), the roton dispersion, the strength of single quasiparticle peak, Z(q), and the static density response function, (q). As the density increases, the dispersion E(q) at low-wave vector changes from a superlinear (anomalous dispersion) trend to a sublinear (normal dispersion) one, anticipating the crystallization of the system; at the same time the maxon–roton structure, which is barely visible at low density, becomes well developed at high densities and the roton wave vector has a strong density dependence. Connection is made with recent inelastic neutron scattering results from highly ordered silica nanopores partially filled with ⁴He.
format Article
author Arrigoni, F.
Vitali, E.
Galli, D.E.
Reatto, L.
author_facet Arrigoni, F.
Vitali, E.
Galli, D.E.
Reatto, L.
author_sort Arrigoni, F.
title Excitation spectrum in two-dimensional superfluid ⁴He
title_short Excitation spectrum in two-dimensional superfluid ⁴He
title_full Excitation spectrum in two-dimensional superfluid ⁴He
title_fullStr Excitation spectrum in two-dimensional superfluid ⁴He
title_full_unstemmed Excitation spectrum in two-dimensional superfluid ⁴He
title_sort excitation spectrum in two-dimensional superfluid ⁴he
publisher Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
publishDate 2013
topic_facet Сверхтекучесть в низкоразмерных системах и в условиях ограниченной геометрии
url http://dspace.nbuv.gov.ua/handle/123456789/118751
citation_txt Excitation spectrum in two-dimensional superfluid ⁴He / F. Arrigoni, E. Vitali, D.E. Galli, L. Reatto// Физика низких температур. — 2013. — Т. 39, № 9. — С. 1021–1030. — Бібліогр.: 37 назв. — англ.
series Физика низких температур
work_keys_str_mv AT arrigonif excitationspectrumintwodimensionalsuperfluid4he
AT vitalie excitationspectrumintwodimensionalsuperfluid4he
AT gallide excitationspectrumintwodimensionalsuperfluid4he
AT reattol excitationspectrumintwodimensionalsuperfluid4he
first_indexed 2023-10-18T20:32:54Z
last_indexed 2023-10-18T20:32:54Z
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