Perturbation Calculation of Band-Structure Effects in Low-Field Helicon Propagation

Abstract

The dispersion relation for low-field helicon propagation in solids with many-valley, ellipsoidal energy surfaces has been calculated in the local limit by a perturbation technique valid to first order in $\frac{\ensuremath{\omega}}{{\ensuremath{\omega}}_{c}}$ and $\frac{1}{{\ensuremath{\omega}}_{c}\ensuremath{\tau}}$, where ${\ensuremath{\omega}}_{c}$ is the cyclotron frequency and $\ensuremath{\tau}$ is the collision time. Collision anisotropy has also been included. The results should be useful not only for understanding band-structure effects in helicon propagation but also for band-structure determination in high-mobility semiconductors and alloys and in doped semimetals, where cyclotron resonance experiments are usually difficult to interpret. In addition to the conditions indicated above, $\ensuremath{\omega}\ensuremath{\tau}\ensuremath{\gtrsim}1$ is required for the first-order perturbation results to be adequate for calculating the real part of the propagation constant.