Giant Quantum Oscillations in the Magnetoacoustic Attenuation of Mercury

Measurements of the magnetoacoustic attenuation have been performed in mercury single crystals at temperatures down to 0.45 K and fields up to 70 kOe. For longitudinal waves in the frequency range 20-70 MHz, the attenuation coefficient exhibits giant quantum oscillations with spikelike character. The attenuation peaks are induced by the $\ensuremath{\beta}$ arms of the first-zone hole surface. Their period in inverse magnetic field is measured as a function of the magnetic field orientation. The particular shape of the attenuation peaks is explained by taking into account the negative value of the effective mass in the magnetic field direction (saddle point). Measurements of the linewidth and height are presented. It is shown that the line suffers an inhomogeneous broadening. The latter is connected with the effect of dislocations on the Landau levels and a line-shape calculation is presented. Unusual line-height properties are reported. The line height depends on the ultrasonic-wave amplitude and in some cases there are attenuation dips instead of attenuation peaks at the same magnetic field values. The peak-height behavior is explained by a magnetic field effect on the electron-dislocation interaction.

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