Photoelectromagnetic Effect Induced by Terahertz Laser Radiation in Topological Crystalline Insulators PbSnTe.

Topological crystalline insulators form a class of semiconductors for which surface electron states with the Dirac dispersion relation are formed on surfaces with a certain crystallographic orientation. PbSnTe alloys belong to the topological crystalline phase when the SnTe content exceeds 0.35, while they are in the trivial phase at < 0.

Non-equilibrium electron transport induced by terahertz radiation in the topological and trivial phases of Hg Cd Te.

Terahertz photoconductivity in heterostructures based on n-type Hg Cd Te epitaxial films both in the topological phase ( < 0.16, inverted band structure, zero band gap) and the trivial state ( > 0.16, normal band structure) has been studied.

Electron energy relaxation under terahertz excitation in (Cd Zn )As Dirac semimetals.

We demonstrate that measurements of the photo-electromagnetic effect using terahertz laser radiation provide an argument for the existence of highly conductive surface electron states with a spin texture in Dirac semimetals (Cd Zn )As. We performed a study on a range of (Cd Zn )As mixed crystals undergoing a transition from the Dirac semimetal phase with an inverse electron energy spectrum to trivial a semiconductor with a direct spectrum in the crystal bulk by varying the composition . We show that for the Dirac semimetal phase, the photo-electromagnetic effect amplitude is defined by the number of incident radiation quanta, whereas for the trivial semiconductor phase, it depends on the laser pulse power, irrespective of wavelength.

Terahertz polarization conversion with quartz waveplate sets.

We present the results of calculation and experimental testing of an achromatic polarization converter and a composite terahertz waveplate (WP), which are represented by sets of plane-parallel birefringent plates with in-plane birefringence axis. The calculations took into account the effect of interference, which was especially prominent when plates were separated by an air gap. The possibility of development of a spectrum analyzer design based on a set of WPs is also discussed.