Modern Physics Letters B

The plastic deformation of dilute alloys is often accompanied by plastic instabilities due to dynamic strain aging and dislocation interaction. The repeated breakaway of dislocations from and their recapture by solute atoms leads to stress serrations and localized strain in the strain controlled tensile tests, known as the Portevin-Le Chatelier (PLC) effect. In this present work, we analyze the stress time series data of the observed PLC effect in the constant strain rate tensile tests on Al-2.5%Mg alloy for a wide range of strain rates at room temperature. The scaling behavior of the PLC effect was studied using two complementary scaling analysis methods: the finite variance scaling method and the diffusion entropy analysis. From these analyses we could establish that in the entire span of strain rates, PLC effect showed Levy walk property. Moreover, the multiscale entropy analysis is carried out on the stress time series data observed during the PLC effect to quantify the complexity of the distinct spatiotemporal dynamical regimes. It is shown that for the static type C band, the entropy is very low for all the scales compared to the hopping type B and the propagating type A bands. The results are interpreted considering the time and length scales relevant to the effect.

We have investigated a different manganese oxide material in which the colossal magnetoresistance (CMR) is observed. As many recent evidences suggest that a superexchange interaction is dominated in the pyrochlore Tl₂Mn₂O₇, it is found that the superexchange interaction is a chief mechanism driving the ferromagnetism. We specially formulate the superexchange interaction to calculate the resistivity in analogy with the t-scattering matrix of the Kondo formalism. We compare our calculation for resistivity with results of experiments and obtain the Curie temperature, T_c.

Utilization of a quantum system whose time-development is described by the nonlinear Schrödinger equation in the transformation of qubits would make it possible to construct quantum algorithms which would be useful in a large class of problems. An example of such a system for implementing the logical NOR operation is demonstrated.

Homogeneous glasses were formed in the Cr₂O₃-TeO₂-B₂O₃-SrF₂ system, up to 20 mol% Cr₂O₃. For these glasses, IR and Raman spectral measurements were carried out in order to elucidate the local structure. The results showed that BO₃ and BO₄ are the main structural units of the glass system and the chromium ions are located in the network. It was evidenced the presence of TeO₃ and TeO₄ units as possible structural units in our glasses.

We present a scheme to generate the tripartite GHZ state via cavity quantum electrodynamics. Our scheme is based on the resonant interaction of a V-type three-level atom with the cavity fields for precalculated interaction time. Also, this scheme can be directly generalized to prepare the general n-qubit GHZ state.

We apply the perturbation theory to investigate the behavior of the Berry phase of a composite system. The composite system consists of two weakly-coupled spin-½ particles, in which each particle is driven by a varying magnetic field. The result shows that the Berry phase for one subsystem is controlled by the state of the other subsystem. The method can also be used to deal with the effect of a spin environment on a single-particle system if the particle is weakly coupled to the spin environment.

The binding energy of a shallow hydrogenic impurity of a spherical quantum dot confined by harmonic oscillator-like and by rectangular well-like potentials, using a variational procedure within the effective mass approximation, has been determined. The calculations of the binding energy of the donor impurity as a function of the system geometry, and the donor impurity position have been investigated. The binding energy of shallow donor impurity depends not only on the quantum confinements but also on the impurity position. Our results reveal that (i) the donor binding energy decreases as the dot size increases irrespective of the impurity position, and (ii) the binding energy values of rectangular confinement are larger than the values of parabolic confinement and (iii) the rectangular confinement is better than the parabolic confinement in a spherical quantum dot.

We introduce new quantum states of light field, called the nonlinear even and odd displaced number states, by introducing the nonlinearity. The statistical properties investigated presents several interesting quantum effects.