International Journal of Modern Physics B

Doping of the lead telluride and related alloys with the group III impurities results in the appearance of unique physical features of the material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We review physical principles of operation of the photodetecting devices based on the group III doped IV–VI including possibilities of fast quenching of the persistent photoresponse, construction of a focal-plane array, new readout technique, and others. Comparison of performance of the state of the art Ge(Ga) and Si(Sb) photodetectors with their lead telluride based analogs shows that the responsivity of PbSnTe(In) photodetectors is by several orders of magnitude higher. High photoresponse is detected at the wavelength of 241 μm in PbSnTe(In), and it is possible that the photoconductivity spectrum covers all the submillimeter wavelength range.

Taking into account the basic physics of diluted ferromagnetic semiconductors (DMS), we use the tunneling Hamiltonian approach to studying the spin-polarized transport in GaMnAs/AlAs/GaMnAs DMS tunnel junctions. It is found that the splitting, Fermi energies, and the hole concentration for a fixed Mn impurity density vary with temperature, which exert a great influence on the spin-polarized transport of the DMS. We have also shown that there exists a spin-flip tunneling process arising from the impurity Mn scattering in the barrier, and the variation of normalized conductance difference ΔG with temperature is consistent with that of experiment.

Structural and dynamical properties of Pd, Ag pure liquid metals and especially Pd_xAg_1-x alloys are studied by the molecular dynamics simulation. The effects of temperature and concentration on the liquid properties of Pd_xAg_1-x are analyzed. Sutton–Chen (SC) and Quantum Sutton–Chen (Q–SC) many-body potentials are used as interatomic interactions. The calculated diffusion constants and viscosities are in good agreement with the available experimental data and theoretical calculations. The coefficients of Arrhenius equation are also presented to calculate the self-diffusion coefficient and shear viscosity of Pd–Ag alloys at the desired temperature and concentration. We have shown that Q–SC potential parameters are more reliable in determining physical properties of metals and their alloys studied in this work.

We reveal that the intensity dependent coupling Hamiltonian via multi-photon interaction in a Kerr medium possesses a supersymmetric structure and therefore can be solved with the supersymmetric transform method. By selecting suitable supersymmetric generators, we derive its energy eigenvalues and eigenvectors.

MnSi_1.73 and MnSi samples were grown by spark plasma sintering (SPS) from different Si/Mn ratio powders, at different sintering temperatures, and for different sintering times. X-ray diffraction (XRD) measurements showed samples containing MnSi and MnSi_1.73 and Si phases, depending on the initial stoichiometries. Measurements of the Seebeck coefficient revealed p-type conductance for all samples. The Seebeck coefficients of the samples with MnSi pure phase were very low (about 10 μ V/K) and changed little at the temperature range measured. The Seebeck coefficients of the samples with MnSi_1.73, MnSi and Si phases were similar to that of the sample with near-pure MnSi_1.73 phase, which were larger than those of the samples with MnSi_1.73 and MnSi phases, but a little smaller than those of the samples with MnSi_1.73 and Si phases. It seems that, for the samples with the same phases, larger ratio of the strongest intensity peak of MnSi_1.73 to , MnSi_1.73 to or both lead to larger Seebeck coeffiecients.

Here we discuss interaction of a single two-level atom with a single mode of interacting electromagnetic field in the Jaynes–Cummings model with the rotating wave approximation.

We obtained the uncertainty relation in squeezed states for a time-dependent oscillator. The uncertainty relation in coherent states is same as that of the number states with n=0. However, the uncertainty relation in squeezed states does not satisfy this property and depends on squeezing parameter c. For instance, the uncertainty relation is ℏ/2 which is the minimum value as far as quantum mechanics permits for c=1, same as that in coherent state for c=±∞, and infinity for c=-1. If the time-dependency of the Hamiltonian for the system vanishes, the uncertainty relation in squeezed states will no longer depend on c and becomes the same as that in number state with n=0, like the uncertainty relation in coherent states.

In this communication we handle a modified model representing the interaction between a two-level atom and two modes of the electromagnetic field in a cavity. The interaction between the modes is assumed to be of a parametric amplifier type. The model consists of two different systems, one represents the Jaynes–Cummings model (atom–field interaction) and the other represents the two mode parametric amplifier model (field–field interaction). After some canonical transformations the constants of the motion have been obtained and used to derive the time evolution operator. The wave function in the Schrödinger picture is constructed and employed to discuss some statistical properties related to the system. Further discussion related to the statistical properties of some physical quantities is given where we have taken into account an initial correlated pair-coherent state for the modes. We concentrate in our examination on the system behavior that occurred as a result of the variation of the parametric amplifier coupling parameter as well as the detuning parameter. It has been shown that the interaction of the parametric amplifier term increases the revival period and consequently longer period of strong interaction between the atom and the fields.

The effect of the position of the off-ramp (way out), on the traffic flow phase transition is investigated using numerical simulations in the one-dimensional cellular automaton traffic flow model with open boundaries using parallel dynamics. When the off-ramp is located between two critical positions i_c1 and i_c2 the current increases with the extracting rate β₀, for β₀<β_0c1, and exhibits a plateau (constant current) for β_0c1<β₀<β_0c2 and decreases with β₀ for β₀>β_0c2. However, the density undergoes two successive first order transitions: from high density to plateau current phase at β₀=β_0c1; and from average density to the low one at β₀=β_0c2. In the case of two off-ramps located respectively at i₁ and i₂, these transitions occur only when i₂-i₁ is smaller than a critical value. Phase diagrams in the (α,β₀), (β,β₀) and (i₁,β₀) planes are established. It is found that the transitions between free traffic (FT), congested traffic (CT) and plateau current (PC) phases are of first order. The first order line transition in (i₁,β₀)-phase diagram terminates by an end point above which the transition disappears.