Study of rotons in superfluid {sup 4}He by Raman scattering

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00754592· OSTI ID:198185

Reatto, L ^[1]

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1. Universita de Milano Via Celoria, Milano (Italy)

There is a long standing disagreement between neutron and Raman scattering from rotons in superfluid {sup 4}He near T{lambda}. In neutron scattering the linewidth becomes very large and the roton signal seems to disappear at T{lambda}. A substantially smaller linewidth is observed with Raman scattering and the roton signal is present even at T{lambda}. We have interpreted this difference as due to a modulation of the roton energy by a fluctuating local superfluid velocity due to proliferation of vorticity as T{lambda} is approached. This gives rise to an extra contribution to the roton linewidth in neutron scattering but not in Raman scattering in which two rotons with almost opposite momenta are excited. We propose a test of this explanation with evanescent field Raman scattering. It has been suggested that in such a measurement the scattering by a single roton should be measurable. In this case the presence of a fluctuating local superfluid velocity should shout lip as in neutron scattering and corroborate our proposal.

• Sponsoring Organization: USDOE
• OSTI ID: 198185
• Report Number(s): CONF-950676--
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 1-2 Vol. 101; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
HELIUM 4
NEUTRON DIFFRACTION
RAMAN EFFECT
ROTORS
SCATTERING
SUPERFLUIDITY