Microscopic dynamics of superfluid ${}^4$He: a comprehensive study by inelastic neutron scattering

Abstract

The dynamic structure factor of superfluid ${}^4$He has been investigated at very low temperatures by inelastic neutron scattering. The measurements combine different incoming energies resulting in an unprecedentedly large dynamic range with excellent energy resolution, covering wave vectors $Q$ up to 5 Å${}^{-1}$ and energies $\omega$ up to 15 meV. A detailed description of the dynamics of superfluid ${}^4$He is obtained from saturated vapor pressure up to solidification. The single-excitation spectrum is substantially modified at high pressures, as the maxon energy exceeds the roton-roton decay threshold. A highly structured multi-excitation spectrum is observed at low energies, where clear thresholds and branches have been identified. Strong phonon emission branches are observed when the phonon or roton group velocities exceed the sound velocity. The spectrum is found to display strong multi-excitations whenever the single-excitations face disintegration following Pitaevskii's type a or b criteria. At intermediate energies, an interesting pattern in the dynamic structure factor is observed in the vicinity of the recoil energy. All these features, which evolve significantly with pressure, are in very good agreement with the Dynamic Many-body calculations, even at the highest densities, where the correlations are strongest.

References in corpus (9)

• Ab-initio low-energy dynamics of superfluid and solid 4He
• Dynamic structure factor of liquid 4He across the normal-superfluid transition
• Roton-Phonon Interactions in Superfluid 4He
• Dynamic Many-Body Theory. II. Dynamics of Strongly Correlated Fermi Fluids
• Theory and data analysis for excitations in liquid ${}^4$He beyond the roton minimum
• Dynamic structure factor for 3He in two-dimensions
• Superfluid 4He dynamics beyond quasiparticle excitations
• Liquid and solid phases of 3He on graphite
• The Momentum Distribution of Liquid ${}^4$He

Cited by in corpus (10)

• The dispersion relation of Landau elementary excitations and the thermodynamic properties of superfluid ${}^4$He
• Dynamical excitation of maxon and roton modes in a Rydberg-Dressed Bose-Einstein Condensate
• Superfluid Optomechanics with Phononic Nanostructures
• Re-examining the quadratic approximation in theory of a weakly interacting Bose gas with condensate: the role of nonlocal interaction potentials
• Variational and parquet-diagram calculations for neutron matter. II. Twisted Chain Diagrams
• Ultrafast non-equilibrium dynamics of rotons in superfluid helium
• Breakdown of sound in superfluid helium
• Transport and Phonon Damping in ${}^4$He
• Chiral vortex-line liquid of three-dimensional interacting Bose systems with moat dispersion
• A Parameter-Free Differential Evolution Algorithm for the Analytic Continuation of Imaginary Time Correlation Functions