Interaction between a tubular beam of charged particles and a dispersive metamaterial of cylindrical configuration.

The interaction between a tubular beam of charged particles and a dispersive metamaterial of cylindrical configuration has been investigated theoretically. This metamaterial may have negative permittivity and negative permeability simultaneously over a certain frequency range where it behaves like a left-handed metamaterial. The dispersion equation for the eigenmodes spectra of a metamaterial and the coupled modes spectra of the system have been derived and numerically analyzed. It has been found that the absolute beam instability of bulk-surface waves occurs because of peculiarities of the eigenmodes spectra of a left-handed metamaterial. Specifically, the resonant frequency behavior of the permeability causes the emergence of the sections of dispersion curves with anomalous dispersion. It has been demonstrated that the symmetric bulk-surface mode with two field variations along the cylinder radius possesses the maximum value of instability increment. The obtained results allow us to propose the left-handed metamaterial as the delaying medium in oscillators of electromagnetic radiation without a need to provide an additional feedback in the system just as in a backward-wave tube.

Conversion of terahertz wave polarization at the boundary of a layered superconductor due to the resonance excitation of oblique surface waves.

We predict a complete TM↔TE transformation of the polarization of terahertz electromagnetic waves reflected from a strongly anisotropic boundary of a layered superconductor. We consider the case when the wave is incident on the superconductor from a dielectric prism separated from the sample by a thin vacuum gap. The physical origin of the predicted phenomenon is similar to the Wood anomalies known in optics and is related to the resonance excitation of the oblique surface waves. We also discuss the dispersion relation for these waves, propagating along the boundary of the superconductor at some angle with respect to the anisotropy axis, as well as their excitation by the attenuated-total-reflection method.

Edge electron states for quasi-one-dimensional organic conductors in the magnetic-field-induced spin-density-wave phases.

We develop a microscopic picture of the electron states localized at the edges perpendicular to the chains in the Bechgaard salts in the quantum Hall regime. In a magnetic-field-induced spin-density-wave state characterized by an integer N, there exist N branches of chiral gapless edge excitations. Localization length is much longer and velocity much lower for these states than for the edge states parallel to the chains. We calculate the contribution of these states to the specific heat and propose a time-of-flight experiment to probe the propagating edge modes directly.