Determination of the Cyclotron Masses of the Conduction Band of Bi 1−x Sb x near the Semimetal‐Semiconductor Transition

In a number of n‐doped Bi 1−x Sb x samples approaching the semimetal‐semiconduct or transition (0.070 ≦ x ≦ 0.083), the propagation of magnetoplasma waves is investigated in the B ⊥ C 2 , ∥ k orientation at 4.2 K. The plane‐parallel samples are prepared from a single crystal exhibiting a slight gradient in the antimony concentration. By means of an ellipsoidal model of the conductivity tensor, the low cyclotron mass m c 2 and the anisotropy m c 3 / m c 2 are determined from the experimental dependence of the wave vector on the frequency and the magnetic field. In the samples with x < 0.073, the dispersion and the attenuation of the waves show peculiarities which can be explained by the presence of holes at the point T. The results obtained indicate a continuous dependence of the band characteristics on the antimony concentration in the neighbourhood of the point x 0 , where the overlapping of the bands at L and T is removed.