Effects of nonellipsoidal nonparabolic band structure on longitudinal magnetoacoustic phenomena in bismuth

Abstract

The effect of the Cohen nonellipsoidal nonparabolic (NENP) band structure on the propagation of ultrasound in bismuth in the presence of a d.c. magnetic field is investigated by using a quantum-mechanical treatment which is valid at high frequencies and in strong magnetic fields. It is found that the absorption coefficient and sound velocity for ultrasound propagating parallel to the d.c. magnetic field depend upon the magnetic field and sound frequency. The dependence on magnetic field arises from the nonlinear effect of the energy bands owing to the NENP model for bismuth, while the dependence on sound frequency is due to the electron-phonon interaction in bismuth. Some oscillations and discontinuities in the absorption coefficient and change in the sound velocity appear in the region of strong magnetic fields and high frequencies. However, the oscillations will be diminished at sound frequencies above omega =2*1011 rad s-1. A brief discussion about the spin-splitting effect in bismuth is made. It shows that the spin-splitting energy cannot be neglected in the region of strong magnetic fields.