Study of elementary excitations of superfluid4He in silica aerogels

The collective excitations of superfluid4He in aerogel glass

“…The Monte-Carlo simulations showed that multiple scattering would not give rise to any excitation broadening. DeKinder et al 26 have also shown that the multiple scattering is due to aerogel-roton scattering by setting their incident neutron energy below the roton energy and showing the extra scattering disappeared. Typical examples of observed experimental data at constant scattering angle ~b, emphasizing the marked temperature variation, are presented in Figs.…”

Phonons, Rotons, and Layer Modes of LiquidH4ein Aerogel

“…Our new neutron scattering measurements using two different neutron spectrometers and two different 87% porous aerogel samples show that there is no difference between the threedimensional (3D) phonon-roton ( p-r) excitation energies and lifetimes of superfluid 4 He in aerogel and in bulk liquid 4 He within current precision. Specifically, the temperature ͑T ͒ dependence of the 3D roton energy, and of other excitation energies, in aerogel is indistinguishable from that in the bulk.…”

“…Disorder and confinement has a profound impact on superfluidity, Bose-Einstein condensation, and phase transitions [1][2][3]. The nature of the excitations in these "dirty Bose systems" in turn plays a key role in determining these properties, and measurements of these excitations by neutron scattering has now begun [4][5][6][7][8][9][10].In this Letter, we present a new picture of the excitations of liquid 4 He in aerogel. Our new neutron scattering measurements using two different neutron spectrometers and two different 87% porous aerogel samples show that there is no difference between the threedimensional (3D) phonon-roton ( p-r) excitation energies and lifetimes of superfluid 4 He in aerogel and in bulk liquid 4 He within current precision.…”

“…Disorder and confinement has a profound impact on superfluidity, Bose-Einstein condensation, and phase transitions [1][2][3]. The nature of the excitations in these "dirty Bose systems" in turn plays a key role in determining these properties, and measurements of these excitations by neutron scattering has now begun [4][5][6][7][8][9][10].…”

Phonon-roton modes of liquid4He beyond the roton in the porous medium MCM-41

“…The dynamical structure factor (DSF), S(Q, ω), of liquid 4 He at saturated vapor pressure (SVP) at lower wave vectors, Q ≤ 2.4Å −1 has been investigated in several porous media; aerogel, [12][13][14][15][16][17][18][19] 33 When the porous media is fully filled, the P-R mode energy in all porous media investigated to date is the same as in bulk superfluid 4 He. This is both at low temperature and as a function of temperature within precision 34 .…”