Anisotropy of Ultrasonic Attenuation Coefficient in Dirty Metals under Strong Magnetic Fields

抄録

In the quantum limit of strong magnetic fields, the electronic polarization function of non-interacting systems is calculated within the ladder approximation for impurity scatterings. The diffusion constants are shown to have strong anisotropy depending on the purity of the sample; i.e. the diffusion constant in the parallel direction to the field is much larger than that in the parpendicular direction. The anisotropy gets stronger as the sample gets purer. Since the polarization function is closely related to the phonon damping, this anisotropy of the diffusion constants leads to that of the ultrasonic attenuation coefficients, which is explicitly calculated for several values of material parameters which may be realized in typical semimetals such as Bi.