Back gating of a two-dimensional hole gas in a SiGe quantum well

A device comprising a low-resistivity, n-type, Si substrate as a back gate to a p-type (boron), remote-doped, SiGe quantum well has been fabricated and characterized. Reverse and forward voltage biasing of the gate with respect to the two-dimensional hole gas in the quantum well allows the density of holes to be varied from 8 × 1011 cm–2 down to a measurement-limited value of 4 × 1011 cm–2. This device is used to demonstrate the evolution with decreasing carrier density of a re-entrant insulator state between the integer quantum Hall effect states with filling factors 1 and 3

Fractional quantum Hall effect without energy gap

In the fractional quantum Hall effect regime we measure diagonal ($\rho_{xx}$) and Hall ($\rho_{xy}$) magnetoresistivity tensor components of two-dimensional electron system (2DES) in gated GaAs/Al$_{x}$Ga$_{1-x}$As heterojunctions, together with capacitance between 2DES and the gate. We observe 1/3- and 2/3-fractional quantum Hall effect at rather low magnetic fields where corresponding fractional minima in the thermodynamical density of states have already disappeared manifesting complete suppression of the quasiparticle energy gaps.Comment: 4 pages, 4 figure

Photon-assisted scattering and magnetoconductivity oscillations in a strongly correlated 2D electron system formed on the surface of liquid helium

The influence of strong internal forces on photon-assisted scattering and on the displacement mechanism of magnetoconductivity oscillations in a two-dimensional (2D) electron gas is theoretically studied. The theory is applied to the highly correlated system of surface electrons on liquid helium under conditions that the microwave frequency is substantially different from inter-subband resonance frequencies. A strong dependence of the amplitude of magnetoconductivity oscillations on the electron density is established. The possibility of experimental observation of such oscillations caused by photon-assisted scattering is discussed.Comment: 7 pages, 1 figur

Universal Behaviour of Metal-Insulator Transitions in the p-SiGe System

Magnetoresistance measurements are presented for a strained p-SiGe quantum well sample where the density is varied through the B=0 metal-insulator transition. The close relationship between this transition, the high field Hall insulator transition and the filling factor $\nu$=3/2 insulating state is demonstrated.Comment: 6 pages, 4 figures. Submitted to EP2DS XIII conference 199

Magnetoresistivity in a Tilted Magnetic Field in p-Si/SiGe/Si Heterostructures with an Anisotropic g-Factor: Part II

The magnetoresistance components $\rho_{xx}$ and $\rho_{xy}$ were measured in two p-Si/SiGe/Si quantum wells that have an anisotropic g-factor in a tilted magnetic field as a function of temperature, field and tilt angle. Activation energy measurements demonstrate the existence of a ferromagnetic-paramagnetic (F-P) transition for a sample with a hole density of $p$=2$\times10^{11}$\,cm$^{-2}$. This transition is due to crossing of the 0$\uparrow$ and 1$\downarrow$ Landau levels. However, in another sample, with $p$=7.2$\times10^{10}$\,cm$^{-2}$, the 0$\uparrow$ and 1$\downarrow$ Landau levels coincide for angles $\Theta$=0-70$^{\text{o}}$. Only for $\Theta$ > 70$^{\text{o}}$ do the levels start to diverge which, in turn, results in the energy gap opening.Comment: 5 pages, 6 figure

The scenario approach to the development of regional waste management systems (Implementation experience in the regions of Russia)

The article illustrates a theoretical approach to scenario modeling of economic indicators of regional waste management system. The method includes a three-iterative algorithm that allows the executive authorities and investors to take a decision on logistics, bulk, technological and economic parameters of the formation of the regional long-term (10-25 years) waste management program. © 2016 Fomin et al

Two-component model of a spin-polarized transport

Effect of the spin-involved interaction of electrons with impurity atoms or defects to the transport properties of a two-dimensional electron gas is described by using a simplifying two-component model. Components representing spin-up and spin-down states are supposed to be coupled at a discrete set of points within a conduction channel. The used limit of the short-range interaction allows to solve the relevant scattering problem exactly. By varying the model parameters different transport regimes of two-terminal devices with ferromagnetic contacts can be described. In a quasi-ballistic regime the resulting difference between conductances for the parallel and antiparallel orientation of the contact magnetization changes its sign as a function of the length of the conduction channel if appropriate model parameters are chosen. The effect is in agreement with recent experimental observations.Comment: 4 RevTeX pages with 4 figure

Issues of financial assurance of economy greening in the regions

The relevance of the analyzed issue is caused by the need to internalize environmental externalities in the modern world. The purpose of the article is to examine the issue of financial support of the green economy using the example of the regions included in the Volga Federal District (VFD). The leading methods to the study of this issue is a comparative analysis of environmental taxes and charges in Russia and countries of the European Union (EU) and the analysis of environmental problems in the regions of the Volga Federal District, which allow identifying the shortcomings of the existing environmental payment system and proposing measures to modernize the system of financial support of the green economy. The key shortcomings of the existing environmental payment system: low rates of environmental payments; the inappropriate use of funds received from environmental payments; concentration of 97% of revenues from environmental payments in the federal budget. The contents of the article may be helpful for public authorities of general and special competence to develop the principal directions of environmental policy and plan activities aimed at improving the green economy. © 2016 Shekhova et al

Teacher’s labour as a tool of forming human capital of higher school graduates

The relevance of the research problem is determined by the intensity of modernization of Russian education, which includes the integration of Western technologies, traditions of the Soviet education and modern requirements to higher education in Russia. The aim of the article lies in justification of one of the most important for Russian education problem of the links between the teacher’s labour and quality of education of higher school graduate. A leading approach to the study of this problem is practice-oriented approach to the training of highly qualified specialists. The following results of the study were obtained: the situation in modern Russian education over the past decade was described, taking into account the change of educational paradigm; the idea that the accumulation of human capital by worker of higher school results in achieving the best results in the formation of students’ competences is justified; the methodology of control the level of formation of competences of university students as a result of the teacher’s labour is presented; the system of evaluating the level of formation of competences of students and graduates of the university is developed, indicators of which, obtained in its implementation in practice, can find application in the evaluation of the results of work of the teaching staff of the University. The article can be useful for researches in the field of education, teachers, postgraduates, undergraduates and students of pedagogical education. © 2016 Dorozhkin et al