Emission and absorption of phonons by rotons in superfluid helium |
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| Authors: | J Jäckle K W Kehr |
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| Institution: | 1. Fachbereich Physik, Universit?t Konstanz, D-775, Konstanz, Germany
2. Institut für Festk?rperforschung, KFA Jülich, D-517, Jülich, Germany
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| Abstract: | The roton spectrum of superfluid helium apparently has a threshold for phonon emission and absorption processes. We calculate
the roton spectral function near the threshold for phonon emission in order to determine the effect of the phonon emission
process on the roton line width. The spectral function develops a line shape anomaly due to a strong energy dependence of
the roton self-energy. The line width is generally smaller than the sum of the phonon emission rate and the roton-roton collision
rate. We also derive the ultrasonic attenuation due to the absorption of phonons by thermal rotons above the threshold. |
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