Magnetophonon resonance in a GaAs quantum well with AlAs/GaAs superlattice barriers at high filling factors

The magnetotransport of a high-mobility 2D electron gas in single GaAs quantum wells with AlAs/GaAs superlattice barriers is studied at high filling factors. For the selectively doped structures under study in the temperature range from 10 to 25 K, magnetoresistance oscillations periodic in the inverse magnetic field are observed with their frequency being proportional to the Fermi wave vector of the 2D electron gas. The experimental results are explained by the interaction of the 2D electron gas with leaky interface acoustic phonons.     

Optical properties of perforated metal-dielectric heterostructures magnetized in the plane

Physics of the Solid State - The magneto-optical properties of perforated metal-dielectric heterostructures that consist of a metal film perforated with a periodic system of slits and a dielectric...     

Transport poperties of a GaAs/AlGaAs ring interferometer in the tunneling regime

The transport properties of GaAs/AlGaAs submicron rings with split gates in the conditions corresponding to the ring resistance R _SD τ;h/e ² are studied. Oscillations of R _SD as a function of the gate voltage V _G are experimentally observed. The oscillations are caused by the single-electron charging of two triangular conducting regions into which the ring is divided in the tunneling regime.     

Field-periodic magnetoresistance oscillations in thin graphite single crystals with columnar defects

The magnetoresistance of thin graphite single crystals with columnar defects has been studied. The field-periodic contribution to the magnetoresistance with a period of 7.5 T has been revealed. The atomic force microscope estimation of the columnar defect diameter shows that the period of the contribution oscillatory as a function of the flux is close to hc/e per defect. The result agrees with the measurements of Aharonov-Bohm magnetoresistance oscillations in graphene mesoscopic rings [S. Russo et al., Phys. Rev. B 77, 085413 (2008)].     

Nonlinear Hall effect in a quasi-two-dimensional electron system

The nonlinear electron transport in GaAs double quantum wells with two occupied size-quantization levels has been studied at a temperature of 4.2 K in the magnetic fields B < 1 T. It has been found that a sinusoidal electric current I _ac induces the generation of higher harmonics of both longitudinal V _xx (B) and Hall V _xy (B) voltages in the quasi-two-dimensional electron system under consideration. The Hall voltage oscillating in the magnetic field has been shown to appear in the electron system with two occupied size-quantization levels in the presence of microwave radiation and dc electric current I _dc. The experimental data indicate the independent contributions of the diagonal and off-diagonal components of the conductivity tensor to the nonlinear magnetotransport at high filling factors.     

ESR study of impurities in strontium titanate films

The paper reports on an ESR study of Cr-and Ca-codoped SrTiO₃ films, 1700 and 350 nm thick, before and after UV irradiation (λ=365 nm). The spectrum of the thick film (1700 nm) exhibits two ESR lines with g factors of 1.977 and 1.974, which belong to the Cr³⁺ centers. In the spectrum of the thin film (350 nm), one observes only one line, which is due to the chromium center with a g factor of 1.974. Calculations showed that the line with the smaller g factor belongs to the Cr³⁺ center located close to the film surface. The weak line observed in the spectrum after UV irradiation (g factor = 2.012) is most likely due to the O^? center. The regions of thermal stability of the observed centers were studied. A comparative analysis of the characteristics of impurities in bulk samples and films was carried out.     

Beats of Quantum Oscillations of the Resistance in Two-Subband Electron Systems in Tilted Magnetic Fields

JETP Letters - Electron transport in single GaAs quantum wells of widths from 22 to 46 nm with two populated quantum-confinement subbands ES and EAS is investigated at a temperature of T = 4.2 K in...     

Constitutive relations of strain, anisotropic degradation, and fracture of filled polymer materials in prevailing-tension processes with varying axis direction and relaxations

In the course of monotone uniaxial tension, filled polymer materials quasi-isotropic in the initial state experience increasing structure fractures (local adhesive separation and cohesive tearing) whose directions are mainly perpendicular to the tension axis. After complete unloading and relaxation, the fracture lips close, and weaker secondary bonds are formed between them. Taking into account the anisotropy of the above-described process of deterioration of the material structure and mechanical properties (degradation), we suggest to characterize the state of each elementary material fiber by its own values of the structure parameters (damage, fracture, and maximum strain), which can be calculated (according to the model equations of uniaxial tension in a constant direction) from the effective strain history of the fiber. It is determined as the product of the current values of two factors, namely, the strain intensity and the influence function, whose argument is the angle between the directions of the fiber under study and the maximum principal strain. The form of the influence function depends on the material and reflects the degree of anisotropy of the damage arising in it. As a model of uniaxial tension in a constant direction, we use the earlier-proposed version of the nonlinear endochronic theory of ageing viscoelastic materials, which, in addition, contains the secondary bond parameter (with its own equation). We show how the proposed constitutive relations permit one to describe the decrease in the resistance and the ultimate strain during the second axial tension compared with a similar tension from the initial state and to determine the dependence of these effects on the angle between the directions of the preliminary and repeated tensions.