Phonon Mediated Roton-Roton Interaction in Superfluid He4

Excitations in superfluid He beyond the roton

– High-energy resolution inelastic neutron scattering data on excitations in superfluid and normal He at SVP at wave vectors Q beyond the roton, 2.0 ≤ Q ≤ 4.0 Å −1 , are presented. The narrow energy resolution of these measurements reveals that the energy of the elementary excitation comes up to twice the roton energy, 2∆, at Q = 2.8 Å −1 and the energy remains constant at 2∆ between Q ' 3.0 Å ...

Phonon-roton modes of liquid 4He beyond the roton in the porous medium MCM-41

R. T. Azuah,1,2 S. O. Diallo,3,* M. A. Adams,4 O. Kirichek,4 and H. R. Glyde3 1NIST Center for Neutron Research, Gaithersburg, Maryland 20899-8562, USA 2Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, USA 3Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716-2593, USA 4ISIS Spallation Neutron Source, Ruth...

Roton-roton crossover in strongly correlated dipolar Bose-Einstein condensates.

We study the pair correlations and excitations of a dipolar Bose gas layer. The anisotropy of the dipole-dipole interaction allows us to tune the strength of pair correlations from strong to weak perpendicular and weak to strong parallel to the layer by increasing the perpendicular trap frequency. This change is accompanied by a roton-roton crossover in the spectrum of collective excitations, f...

Landau phonon-roton theory revisited for superfluid helium 4 and Fermi gases

Phonon-roton excitations in liquid 4He at negative pressures.

We present neutron scattering measurements of the phonon-roton excitations of superfluid 4He held at negative pressures from zero to -5 bar. The liquid was stretched to negative pressures by immersing it in the porous medium MCM-41. In the wave vector range 0.35< or =Q< or =1.55 A(-1) and temperature T=0.4 K investigated, the phonon and maxon energies decrease systematically below bulk values a...