Quantum Monte Carlo study of the dynamic structure factor in the gas and crystal phase of hard-sphere bosons

Year: 2013

Authors: Rota R., Tramonto F., Galli D.E., Giorgini S.

Autors Affiliation: Dipartimento di Fisica, Universitą di Trento and INO-CNR BEC Center, 38123 Povo, Trento, Italy; Dipartimento di Fisica, Universitą degli Studi di Milano, via Celoria 16, 20133 Milano, Italy

Abstract: We investigate the dynamic structure factor of a system of Bose particles at zero temperature using quantum Monte Carlo methods. Interactions are modeled using a hard-sphere potential of size a and simulations are performed for values of the gas parameter na(3) ranging from the dilute regime up to densities n where the thermodynamically stable phase is a solid. With increasing density, we observe a crossover of the dispersion of elementary excitations from a Bogoliubov-type spectrum to a phonon-maxon-roton curve and the emergence of a broad multiphonon contribution accompanying the single-quasiparticle peak. In particular, for na(3=) 0.2138, which corresponds to superfluid He-4 at equilibrium density, the extracted spectrum turns out to be in good agreement with the experimental energy-momentum dispersion relation in the roton region and for higher momenta. The behavior of the spectral function at the same density in the stable solid and metastable gas phase above the freezing point is also discussed.

Journal/Review: PHYSICAL REVIEW B

Volume: 88 (21)      Pages from: 214505-1  to: 214505-11

More Information: We would like to acknowledge L. P. Pitaevskii and L. Reatto for useful discussions. This work has been supported by Regione Lombardia and CINECA Consortium through a LISA Initiative (Laboratory for Interdisciplinary Advanced Simulation) 2012 grant [http://www.hpc.cineca.it/services/lisa], by ERC through the QGBE grant, and by Provincia Autonoma di Trento. Partial support by the Italian MIUR under Contract Cofin-2009 Quantum gases beyond equilibrium is also acknowledged. We thank the Aurora-Science project (funded by PAT and INFN) for allocating part of the computing resources for this work and for technical support.
KeyWords: Integral Ground-state; Homogeneous Bose-gas; Many-body Problem; Zero-temperature; Condensed Helium; Path-integrals; Liquid; Computation; Transition; Propagator
DOI: 10.1103/PhysRevB.88.214505

Citations: 15
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