Magnetoacoustic Attenuation in Semimetals. I. Extraordinarily Large Attenuation Peak in Bismuth forq∧H∼90°

The sound attenuation in bismuth at low temperature has been measured under the conditions: the longitudinal sound wave vector q is applied along the trigonal axis and the field H is parallel to a trigonal-bisectrix plane. For q ∧ H =88.0°±0.3° and 92.2°±0.3°, a quite large attenuation peak has been found, which is due to the second and third lowest Landau levels of the electrons in the degenerated non-principal electron pockets. Its attenuation coefficient α( T , H p ) shows fairly strong temperature dependence and frequency dependence as compared with those in other orientations. A theoretical analysis is presented to explain a part of the anomalies.