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Persistent URL http://purl.org/net/epubs/work/37159
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Record Id 37159
Title High-resolution roton spectra around the superfluid transition temperature in liquid He-4
Abstract We show for the first time high-resolution excitation spectra of bulk superfluid and liquid He-4 obtained in a wide energy range (0-3 meV) in a broad temperature interval 0.6-2.5 K. The experiments were performed at 0.4 bar constant liquid pressure on the time-of-flight crystal analyser neutron spectrometer IRIS at the ISIS Facility.,There is a real gap in resolution between neutron spin echo or exact-backscattering spectroscopy and other conventional time-of-flight or triple-axis-spectrometer measurements, which at the moment can only be covered by IRIS. The unique combination of high resolution and wide dynamic range accessible on this inverted geometry spectrometer allowed for a non-conventionally detailed line-shape analysis of the roton excitations and made possible the separation of the roton and the higher-energy broad components. We provide the high-resolution evidence of a remainder single-phonon response at the extrapolated roton energy above T-lambda. We conclude that the superfluid phase transition manifests itself in the strong slowdown of the variation of the single-phonon line shape with increasing temperature, rather than in the total disappearance of the signal. (c) 2006 Elsevier B.V. All rights reserved.
Organisation CCLRC , ISIS , ISIS-IRIS
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Language English (EN)
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Journal Article Physica B 388, no. 1-2 (2007): 43-48. doi:10.1016/j.physb.2006.04.042 2007