Isoenergy Surface Research Articles

Dielectric Properties of Bi1−xSbx Alloys at the Semiconductor‐Semimetal Transition

AbstractThe composition dependence of the lattice dielectric constant of semiconducting Bi1−xSbx alloys is investigated by means of helicon wave propagation for B∥C1 in high magnetic fields in the neighbourhood of the semiconductor‐semimetal transition. In contrast to the smooth variation of the parameters of the isoenergy surface of the electrons, in the neighbourhood of the transition first a rapid increase of the dielectric constant is observed, followed by a discontinuous drop when the band overlap begins. The comparison with theoretical calculations allows the conclusion that the lattice dielectric constant must be correlated with the indirect band gap of the alloy – the parameter of the semiconductor‐semimetal transition.

Fermi Surface and Helicons in Semiconducting Bi1−xSbx Alloys

AbstractIn semiconducting n‐and p‐type Bi1−xSbx alloys, the propagation of helicons is observed at 35.5 GHz and helium temperatures. Besides the propagation of helicons in the asymptotic limit, helicons are detected also under the influence of time dispersion. Under the influence of time dispersion, the anisotropy of the isoenergy surface of the charge carriers substantially influences the dispersion of helicons. On the basis of this effect we are able to gain information on the Fermi surface and to confirm results obtained from previous cyclotron resonance measurements. The influence of the anisotropy of the isoenergy surface is shown for magnetic fields parallel to special directions of the crystal lattice. This influence can, however, also be found in the anisotropy of the field values of the spatial resonances of the helicon waves.

Magnetoplasma effects in semiconducting Bi1–xSbx alloys

AbstractThe magnetic‐field‐dependent microwave absorption is measured in semiconducting Bi1–xSbx alloys in the frequency ranges of 36 and 70 GHz at helium temperatures. In addition to cyclotron resonance, tilted orbit resonance ist observed. A theoretical lineshape analysis is carried out. The comparison with the experiment shows good agreement. Moreover the hybrid resonance and the dielectric anomaly are discussed and their influence on the magnetic‐field‐dependent microwave absorption in the present material is investigated. The results can in effect be understood on the basis of a model of the isoenergy surface, which is composed of three ellipsoidal parts. Moreover there are indications of deviation from this model.