Magnetoacoustic Attenuation in Semimetals. III. Enhancement of Quantum Oscillations in Bismuth-Antimony Alloys for q∧H∼90°

Abstract

The sound attenuation in Bi_1−xSb_x alloys has been measured under the condition that the magnetic field vector H is nearly perpendicular to the sound wave vector q. Quite unlike bismuth, the quantum oscillations with very large amplitudes and with the line shape like the density of state curve were observed. Particularly, for q parallel to a bisectrix axis, the oscillations take the form of a deep dip whenever the Landau level crosses the Fermi level. These anomalies are compared with a tentative theory taking into account of an effect of random diffractions of the sound wave propagation direction due to a spatial inhomogeneity of antimony concentration. The large humps can be partially explained by the theory but the deep dips cannot be explained at all.