arXiv subjects

F. Dalfovo

Publications and source records attributed to F. Dalfovo.

41 records · Page 3Linked to original sources

arXiv1994

Dispersion of Ripplons in Superfluid 4he

A detailed study of the dispersion law of surface excitations in liquid \hef at zero temperature is presented, with special emphasis to the short wave length region. The hybridization mechanism between surface and bulk modes is discussed on a general basis, investigating the scattering of slow rotons from the surface. An accurate density functional, accounting for backflow effects, is then used to determine the dispersion of both bulk and surface excitations. The numerical results are close to the experimental data obtained on thick films and explicitly reveal the occurrence of important hybridization effects between ripplons and rotons.

cond-mat↗

arXiv1994

Variational Calculations for $^3$He Impurities on $^4$He Droplets

Variational Monte Carlo method is used to calculate ground state properties of $^4$He droplets, containing 70, 112, 168, 240, 330, and 728 particles. The resulting particle and kinetic energy densities are used as an input in the Feynman-Lekner theory for $^3$He impurities. The kinetic energy density of $^4$He atoms and the energy of the $^3$He surface states are compared with the results of previous phenomenological calculations.

cond-mat↗

arXiv1993

Atomic and Molecular Impurities in $^4$He Clusters

A density functional theory is used to predict the binding energy of atomic and molecular impurities (Ne, Ar, Kr, Xe, Li, Na, K, Rb, Cs, and SF$_6$) in the center of $^4$He clusters, in the limit of zero temperature and for zero angular momentum states. The size dependence of the binding energy, from small clusters to the bulk liquid limit, is investigated. The behaviour of the $^4$He density near the impurity is also studied.

cond-mat↗

arXiv1993

Dynamic Structure Function in 3he-4he Mixtures

Relevant features of the dynamic structure function $S(q,ω)$ in $^3$He-$^4$He mixtures at zero temperature are investigated starting from known properties of the ground state. Sum rules are used to fix rigorous constraints to the different contributions to $S(q,ω)$, coming from $^3$He and $^4$He elementary excitations, as well as to explore the role of the cross term $S^{(3,4)}(q,ω)$. Both the low-$q$ (phonon-roton $^4$He excitations and 1p-1h $^3$He excitations) and high-$q$ (deep inelastic scattering) ranges are discussed.

cond-mat↗

arXiv1992

Static Response Function for Longitudinal and Transverse Excitations in Superfluid Helium

The sum rule formalism is used to evaluate rigorous bounds for the density and current static response functions in superfluid helium at zero temperature. Both lower and upper bounds are considered. The bounds are expressed in terms of ground state properties (density and current correlation funtions) and of the interatomic potential. The results for the density static response significantly improve the Feynman approximation and turn out to be close to the experimental (neutron scattering) data. A quantitative prediction for the transverse current response is given. The role of one-phonon and multi-particle excitations in the longitudinal and transverse channels is discussed. (Phys.Rev.B, in press)

cond-mat↗