Dielectric and photoelectric properties of Pb(Mg1/3Ta2/3O3 crystals

The temperature dependence of the dielectric constant ɛ and the spectral dependence of the photoconductivity of Pb(Mg_1/3Ta_2/3)O₃ crystals are investigated. The width of the band gap (3.4 eV) is determined. It is found that above the temperature of the maximum of the dielectric constant, its reciprocal 1/ɛ varies with temperature first quadratically and then according to a linear law, as is characteristic of ferroelectrics with a smeared phase transition. The smearing parameter of the transition estimated from the experimental data is close to the value calculated assuming the absence of long-range order in the arrangement of the Mg and Ta ions. Fiz. Tverd. Tela (St. Petersburg) 40, 109–110 (January 1998)     

Study of the effects of size quantization in coupled AlxGa1? x As/GaAs/Alx Ga1? x as quantum wells by means of photoreflectance spectroscopy

Photoreflectance spectra are measured in heterostructures with coupled quantum wells at room temperature. The energies of the optical transitions are determined, and their variation with the well width and barrier thickness is studied. The experimental results are compared with the theoretically calculated electron-hole transition energies. Good agreement is obtained for narrow wells. __________ Translated from Optika i Spektroskopiya, Vol. 93, No. 6, 2002, pp. 929–934. Original Russian Text Copyright ? 2002 by Avakyants, Bokov, Galiev, Kaminskiĭ, Kul’bachinskiĭ, Mokerov, Chervyakov.     

Determination of the carrier concentration in doped <Emphasis Type="Italic">n</Emphasis>-GaAs layers by Raman and light reflection spectroscopies

The carrier concentrations in Si-doped n-GaAs films have been determined by Raman and light reflection spectroscopies. The data obtained are in good agreement with the results of Hall measurements. It is shown that the light reflection and Raman spectroscopies supplement each other in determination of carrier concentrations in the range 10¹⁷?10¹⁹ cm^?3.     

Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Dependence of the domain-wall velocity on the driving field in garnet films

The dependence of the domain-wall velocity on the amplitude of the driving magnetic field pulses is investigated in an iron garnet film of the (YSmCa)₃(FeGe)₅O₁₂ system with a (111) orientation. The results obtained are analyzed from the standpoint of existing theory. A maximum corresponding to the disruption of steady-state motion is observed on the dependence. Thereafter, the velocity at first decreases sharply and then increases. It is theorized that a process involving the periodic generation, propagation, and annihilation of horizontal Bloch lines occurs in the wall in this period. Data are obtained for the velocity saturation region, which confirm a previously proposed empirical formula and a theoretical model, according to which the saturation regime corresponds to a state of chaos. Fiz. Tverd. Tela (St. Petersburg) 39, 660–663 (April 1997)