Observation of zero-sound at atomic wave-vectors in a monolayer of liquid 3He

Henri Godfrin (1) , Matthias Meschke (2) , Hans-J. Lauter (3) , Helga M. Böhm (4) , Eckhard Krotscheck (4) , Martin Panholzer (4)

1 NEEL - UBT - Ultra-basses températures
2 Aalto - Aalto university low temperature physics
3 ILL - Institut Laue-Langevin
4 Institute for Theoretical Physics [Linz]

The elementary excitations of a strongly interacting two-dimensional Fermi liquid have been investigated by inelastic neutron scattering in an experimental model system: a monolayer of liquid3He adsorbed on graphite preplated by a monolayer of solid 4He. We observed for the first time the particle-hole excitations characterizing the Fermi liquid state of two-dimensional liquid 3He, and we were also able to identify the highly interesting zero-sound collective mode above a particle-hole band. Contrarily to bulk 3He, at low wave-vectors this mode lies very close to the particle-hole band. At intermediate wave-vectors, the collective mode enters the particle-hole band, where it is strongly broadened by Landau damping. At high wave-vectors, where the Landau theory is not applicable, the zero-sound collective mode reappears beyond the particle hole band as a well defined excitation, with a dispersion relation quite similar to that of superfluid 4He. This spectacular effect is observed for the first time in a Fermi liquid (including plasmons excitations in electronic systems).

Mots clés: Quantum fluids; 3He; Fermi Liquid; excitations; inelastic neutron scattering

Domaines: Electrons fortement corrélés [cond-mat.str-el]

Henri Godfrin, Matthias Meschke, Hans-J. Lauter, Helga M. Böhm, Eckhard Krotscheck, et al.. Observation of zero-sound at atomic wave-vectors in a monolayer of liquid 3He. Journal of Low Temperature Physics, 2010, 158, pp.147. ⟨10.1007/s10909-009-9952-5⟩. ⟨hal-00921371⟩