Synthesis and properties of AlBeB22 crystals

Platelike single crystals of aluminum boroberyllide (AlBeB₂₂) with a tetragonal structure are produced from a solution in the Al melt. The crystal structure of the compound is determined, and the microhardness, refractive index dispersion, reflection spectrum, and photoconductivity are measured at 300 K.     

Bose glass and superfluid phase transitions of exciton-polaritons in GaN microcavities

Microcavity exciton-polaritons within GaN-based structures are the object of the present work. The impact of the structural imperfections on the properties of the two-dimensional polariton gas is investigated through the calculation of its phase diagram. We demonstrate that the presence of disorder first induces a quasi-phase transition of the polariton system towards a Bose-glass phase before it becomes superfluid as its density increases. Calculations of the density of states as well as the condensate wavefunction and the related spectrum of elementary excitations in the framework of the Gross-Pitaevskii theory provide further insight into the properties of exciton-polaritons in GaN-based microcavities.     

Bose glass and superfluid phases of cavity polaritons

We report the calculation of cavity exciton-polariton phase diagram including realistic structural disorder. With increasing density polaritons first undergo a quasiphase transition toward a Bose glass: the condensate is localized in at least one minimum of the disorder potential. A further increase of the density leads to a percolation process of the polariton fluid giving rise to a Kosterlitz-Thouless phase transition toward superfluidity. The spatial representation of the condensate wave function as well as the spectrum of elementary excitations are obtained from the Gross-Pitaevskii equation for all the phases.     

Nonlinear terahertz emission in semiconductor microcavities

We consider the nonlinear terahertz emission by the system of cavity polaritons in the regime of polariton lasing. To account for the quantum nature of terahertz-polariton coupling, we use the Lindblad master equation approach and demonstrate that quantum microcavities reveal a rich variety of nonlinear phenomena in the terahertz range, including bistability, short terahertz pulse generation, and terahertz switching.     

Polarization and propagation of polariton condensates

With the use of the generalized Gross-Pitaevskii equation it is shown that exciton polaritons in semiconductor microcavities form a linearly polarized condensate having two branches of the excitation spectrum. The splitting between these branches is strongly anisotropic. This anisotropy noticeably affects the real-space dynamics of polariton condensates.     

Doping of PbTe and Pb1−xSnxTe with gallium and indium

Precipitations in Indium and Gallium-doped PbTe, SnTe and Pb_1−xSn_xTe are investigated. The compositions of the precipitated phases are PbGa₆Te₁₀ SnGa₆Te₁₀ and PbIn₆Te₁₀ for binary compounds. For Pb_1−xSn_xTe the precipitated phase composition corresponds to the continuous solid solutions Pb_1−zSn_zGa₆Te₁₀. Basic properties of the new compounds are determined. Their resistivity being of 5 ÷ 6 orders higher than that for Pb(Sn)Te, the anomalous transfer phenomena, observed in highly Ga(In)-doped samples can be explained on the basis of the barrier model.