Temperature and Frequency Dependence of Longitudinal Sound in HCP 4He
We present here data on the temperature- and frequency-dependence of the longitudinal sound velocity of single crystals of hcp 4He. The data show the following: the longitudinal sound velocity has very large dispersion at all temperatures from the melting point on down; the anomalous behavior is not always present; in crystals that show an anomaly (the majority of those grown), the anomaly moves to lower temperatures with increasing frequency.
KeywordsPhase Velocity Sound Velocity Anomalous Behavior Orientation Dependence Anomalous Dispersion
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