Modern Physics Letters B

We briefly discuss various applications of the Chalker–Coddington network model, starting with the original one, proposed to describe inter-plateaux transition in the integer quantum Hall effect (IQHE). Next, we present generalization appropriate for the IQHE allowing to include spin, and conclude with recent applications to dirty superconductors. We then describe how numerical calculations on an open network produce data for the localization length behavior in the metal-insulator transition, whereas calculations on the closed system allow elucidation of various levels statistics. We also discuss how numerical algorithm for systems with additional symmetries is modified in order to improve the accuracy. Finally, results for the nearest-neighbor spacing distribution in dirty superconductors are presented.

The reconstruction of quantum states of electromagnetic fields is an active research field in modern physics. This paper presents a brief review on this issue. Our review includes the theoretical proposals and experimental measurements on the reconstruction of quantum states of traveling fields and cavity fields. For traveling fields and cavity fields, we discuss the one-mode, two-mode, and multi-mode cases, respectively.

To detect the spin injection efficiency η from a ferromagnet metal (FM) to a semiconductor (SC) in an FM/SC tunnel junction, we propose to introduce another similar single junction to form an FM/SC/FM double tunnel junction, and to measure its tunneling magnetoresistance (TMR). It is found that there is an approximate relation TMR = η² in the sequential tunneling region and at low bias voltage. As the thickness of the middle SC layer is decreased to the extent so that the size of the entire structure is smaller than the electronic coherence length, both coherent tunneling conductance and resonant TMR exhibit oscillating behavior.

Theoretical investigations of spin polaron in a quantum dot in the "spin doping" superlattice systems Cd_{1 - Xin}Mn_XinTe/Cd_{1 - Xout}Mn_XoutTe are presented. We estimated the donor ionization energy by variational technique and the spin polaronic shift using the mean field theory with modified Brillouin function. Our results show that significant enhancement of donor ionization energy and spin polaronic shift occur in a dot when compared to a quantum well, wire and bulk systems.

The influence of the built-in electric field on the low-frequency current fluctuations in n-type non-degenerate homogeneous semiconductors at presence of constant external electric and magnetic fields is examined. The problem is considered by means of Langevin-type Boltzmann transport equations for the electron and phonon systems at domination of electron–acoustic phonon scatterings. For the first time, it is shown that within the context of the introduced problem, the spectral density of the current noise contains 1/f component specified by the built-in electric field. By form it is similar to the empiric Hooge formula. On the basis of the computations, a model explaining the physical mechanism of the origin of the additional component of 1/f noise, conditioned by the presence of the built-in electric field in semiconductor, is proposed. For the Hooge parameter, a comparison with the experimental data of generally observed 1/f noise for Si samples is carried out. The comparison shows that at some "favorable" conditions, the level of this new component of the 1/f noise can reach the level of the generally observed 1/f noise.

Direct optical absorption of light in cylindrical quantum dot was theoretically investigated. Analytical expressions for light absorption coefficients were found for two regimes of size quantization: strong and weak. The corresponding selection rules for optical transitions are defined. The expressions for absorption threshold frequencies are found. The obtained results are compared with the case of light direct optical absorption in spherical quantum dot.