EMP is funded through the Horizon2020 programme of the European Commission.
Selected Publications

Superfluid 4He dynamics beyond quasiparticle excitations

K. Beauvois, C. E. Campbell, J. Dawidowski, B. Fåk, H. Godfrin, E. Krotscheck, H.-J. Lauter, T. Lichtenegger, J. Ollivier, A. Sultan

The dynamics of superfluid 4He at and above the Landau quasiparticle regime is investigated by high-precision inelastic neutron scattering measurements of the dynamic structure factor. A highly structured response is observed above the familiar phonon-maxon-roton spectrum, characterized by sharp thresholds for phonon-phonon, maxon-roton, and roton-roton coupling processes. The experimental dynamic structure factor is compared to the calculation of the same physical quantity by a dynamic many-body theory including three-phonon processes self-consistently. The theory is found to provide a quantitative description of the dynamics of the correlated bosons for energies up to about three times that of the Landau quasiparticles.

Phys. Rev. B 94 (2016) 024504

doi: /10.1103/PhysRevB.94.024504