Modern Physics Letters B

Optical absorption spectrum of Cr⁴⁺ ion in Rb₂CrF₆ is analyzed using the exchange charge model of crystal field theory. The crystal field parameters acting on the optical electrons of Cr⁴⁺ are calculated using the crystal structure data; a good agreement between the calculated and observed energy levels of Cr⁴⁺ in the title host is demonstrated. The crystal field strength Dq=2159 cm^-1 and Racah parameters B=639 cm^-1, C=3605 cm^-1 were evaluated from the experimental spectrum.

Nematic liquid crystal cells were subjected to different DC magnetic fields and the optical transmission of a He-Ne laser beam was recorded for different field values. It was found that a small addition of Methyl Orange (MO) induced optical activity into the nematic sample. When the cells were subjected to increasing magnetic field, the rotatory power (rotation angle) varied periodically; the same occurred for the light transmission and ellipticity. We found that the light emerging from the liquid crystal cell is elliptically polarized and in some cases circularly polarized. After UV light irradiation (365 nm) the rotatory power of the sample increases. The position of rotation angle maxima and minima is slightly affected by the irradiation.

We propose a new method to strengthen the nonlinear pulses robustness to polarization mode dispersion in the conventional lossy fiber systems. The method is based on the generation of the stable trapped state of polarization solitons in an initial optical fiber with high birefringence. It is proven that the obtained bound state of nonlinear pulses have stronger adaptive abilities to polarization mode dispersion than common solitons when they propagate in conventional fibers with random birefringence.

We examine a class of (1+1)-dimensional Dirac equations with an effective mass. It is shown that for a wide choice of the mass function, exact analytical solutions can be obtained for this class of Dirac equations.

Based on Feynman's explanation about the Cooper pair that "a bound pairs act as a Bose particle" and the bosonic operator Hamiltonian of Josephson junction (H.-Y. Fan, Int. J. Mod. Phys. B17 (2003) 2599) as well as the entangled state representation, we establish a possible number–phase squeezing mechanism for the Cooper-pair and the phase difference between the two sides of the junction. We find that when an extra energy (e.g. microwave radiation) is provided to the junction, then this squeezing mechanism can happen.

Nanocrystal indium tin oxide (ITO) thin films were grown by electron beam evaporation (e-beam). The ITO films were fabricated at substrate temperatures ranging from 100 to 400°C in O₂ partial pressure ranging from 0.10 to 100 mTorr. The surface morphology was monitored using atomic force microscopy (AFM). The charge in the surface morphology of ITO films was discussed in terms of grain size and crystallographic orientations. Grain size measurements of the solid dispersed and the AFM study for nanostructure showed that the oxides were in the nano range (20–30 nm). In general, the values of the optical bandgap for the films are consistently blue-shifted as compared with the crystal size. The average crystalline size determined from the shift of the optical gap were found to be in the range 20–30 nm, which is in excellent agreement with the data obtained from AFM. All ITO films average grain size was ~ 20 nm deposited by e-beam evaporation. The average optical transmittance was 90.50% in the visible range (400–700 nm) and the average bandgap was 3.98 eV. ESR spectrum of ITO film showed random oxygen vacancies which arise due to the changing crystal field effects.

Intrinsic decoherence in the thermodynamic limit is shown for a large class of many-body quantum systems in the unitary evolution in NMR and cavity QED. The effect largely depends on the inability of the system to recover the phases. Gaussian decaying in time of the fidelity is proved for spin systems and radiation-matter interaction.

A recent Bose–Einstein condensation (BEC) model of several cuprate superconductors is based on bosonic Cooper pairs (CPs) moving in 3D with a quadratic energy-momentum (dispersion) relation. The 3D BEC condensate-fraction versus temperature formula poorly fits penetration-depth data for two cuprates in the range 1/2<T/T_c≤1 where T_c is the BEC transition temperature. We show how these fits are dramatically improved, assuming cuprates to be quasi-2D, and how equally good fits are obtained for conventional 3D and quasi-1D nanotube superconducting data, provided the correct linear CP dispersion is assumed in BEC at their assumed corresponding dimensionalities. This is offered as additional concrete empirical evidence for linearly-dispersive pairs in another recent BEC scenario of superconductors within which a BCS condensate turns out to be a very special case.