Magnetic Landau damping in aluminum

The effect of collisionless absorption by electrons on the damping of wave modes in aluminum has been theoretically investigated in the geometry where a propagation vector $\mathbf{k}$ and a constant magnetic field $\mathbf{H}$ are directed along the $C_4$ axis. In this geometry, there is a magnetic Landau damping caused by electrons whose orbits are inclined to the transverse plane. It has been shown that this damping can have a significant influence on the spectrum and damping of a helicon near the threshold and on the damping of a thresholdless hole doppleron, the field of which rotates in the direction opposite to the direction of rotation of holes. It has been found that the trapping of electrons by a magnetic field of the large-amplitude radio-frequency wave decreases the efficiency of the absorption. This leads to nonlinear changes in the velocity and damping of a helicon near the threshold and to a change in the damping of the thresholdless doppleron.