Microscopic dynamics of superfluid 4He: A comprehensive study by inelastic neutron scattering

• Autores: Beauvois, K.; Dawidowski, Javier; Fåk, B.; Godfrin, H.; Krotscheck, E.; Ollivier, J.; Sultan, A.
• Año de publicación: 2018
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: HELIO 4; SUPREFLUIDOS; DINÁMICA Y ESTRUCTURA DE LÍQUIDOS
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

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 ω up to 15 meV. A detailed description of the dynamics of superfluid 4He 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 multiexcitation spectrum is observed at lowenergies, 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 multiexcitations 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.
Fil: Beauvois, K.. Universite Grenoble Alpes. Institut Nanosciences et Cryogenie - Commissariat a L´Energie Atomique et Aux Energies Alternatives. Institut Nanosciences et Cryogenie; Francia. Institut Laue Langevin; Francia
Fil: Dawidowski, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina
Fil: Fåk, B.. Institut Laue Langevin; Francia
Fil: Godfrin, H.. Universite Grenoble Alpes. Institut Nanosciences et Cryogenie - Commissariat a L´Energie Atomique et Aux Energies Alternatives. Institut Nanosciences et Cryogenie; Francia
Fil: Krotscheck, E.. State University of New York; Estados Unidos
Fil: Ollivier, J.. Institut Laue Langevin; Francia
Fil: Sultan, A.. Universite Grenoble Alpes. Institut Nanosciences et Cryogenie - Commissariat a L´Energie Atomique et Aux Energies Alternatives. Institut Nanosciences et Cryogenie; Francia