REEMERGENCE OF THE COLLECTIVE MODE IN <sup>3</sup><font>HE</font> AND ELECTRON LAYERS

Böhm, Helga M.; Holler, Robert A.; Krotscheck, E.; Panholzer, Martin; Godfrin, H.; Meschke, Matthias; Lauter, Hans-Jochen

doi:10.1142/9789814340793_0001

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“…The theory builds upon exactly the notion that the physical mechanisms are, in correlated bosonic and fermionic systems, basically the same and, hence, generalizes the time-honored theory of pair fluctuations to fermions by including twoparticle excitations. In a companion article [24], a descrition of the theory is given, as well as a comparison with some of our experimental data. The key result of this joint experimental and theoretical effort is a detailed picture of a model Fermi liquid well beyond the Landau validity domain [19].…”

Section: Resultsmentioning

confidence: 99%

Observation of Zero-Sound at Atomic Wave-Vectors in a Monolayer of Liquid 3He

et al. 2009

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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 liquid 3 He adsorbed on graphite preplated by a monolayer of solid 4 He. We observed for the first time the particle-hole excitations characterizing the Fermi liquid state of two-dimensional liquid 3 He, and we were also able to identify the highly interesting zero-sound collective mode above a particle-hole band. Contrarily to bulk 3 He, 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 particlehole band as a well defined excitation, with a dispersion relation quite similar to that of superfluid 4 He. This spectacular effect is observed for the first time in a Fermi liquid (including plasmons excitations in electronic systems).

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Section: Resultsmentioning

confidence: 99%