Yu. V. Shikina

On the initial stage of spinodal decomposition

A consistent theory describing the initial stage of spinodal decomposition of a two-component system is proposed. It is shown that the structure factor S(q, t) has two maxima as a function of wavenumber at this stage. The main maximum point q+ varies with time, first moving from qsaddle to qm (given by expressions (22) and (12), respectively) and then back after the turning point in time given by (26) is passed. The other maximum point is localized at q ≈ 0, and the corresponding peak amplitude is virtually independent of time. The characteristics of the main maximum are sensitive to the existence of the “zero” peak. Available experimental observations support the predictions of the theory.

On the constriction of the Hall current in the Corbino disk under quantum Hall effect conditions

Modification of the theory describing the current-voltage characteristics of the shielded Corbino disk with spinless two-dimensional (2D) electron system under a magnetic field for nearly integer filling factors in the case of a weak pulling electric field (i.e., its energy being much lower than the cyclotron energy) is suggested. Features of the I-V characteristics in the limits of “pure” and “dirty” 2D electron system are considered. The results are compared with experimental data. Local parameters characterizing the disk with flowing current that can be measured via a linear electrooptical effect (distribution of the 2D electron density, and electric and electrochemical potentials) are determined.

Contact phenomena in 2D electronic systems with an integer filling factor

An interpretation of the available experimental data on the linear electrooptical effect in two-dimensional (2D) electronic systems in quantized magnetic fields has been proposed. The self-consistent treatment of the data obtained for the Corbino and Hall samples in both equilibrium and transport-current-carrying states is performed with due regard for the contact phenomena observed during sample preparation. The limiting cases of small and large contact-potential differences as compared to the cyclotron energy are analyzed.

Multichannel Hall effects in 2D electron systems

A description of available experimental data on the linear electrooptical effect in 2D electron systems exhibiting the quantum Hall effect is proposed. Allowance for the contact effects accompanying preparation of the Corbino discs and the Hall samples provides consistent description of the phenomena observed in the equilibrium state and in a state involving transport current. The contact potentials appear to have a rather large characteristic magnitude that is considerably greater than the cyclotron energy in the experiments being considered. Under these conditions, a large number of the so-called incompressible channels inevitably appear in the samples. The proposed phenomenological description of this “band” state is in qualitative agreement with available experiments.

Contribution to the theory of “incompressible” regions in an inhomogeneous magnetized 2D electronic system

A modification of the theory of “incompressible” regions in an ideal spinless inhomogeneous magnetized 2D electronic system near points on the electron density profile n(x) with an integer filling factor is proposed. Such regions leads to the appearance of a finite capacitance between the parts of the 2D system that are separated by an incompressible channel, so that capacitive methods can be used to investigate such a system. The Corbino configuration is especially convenient for these purposes. The parameters of the “incompressible” channel in a Corbino disk with a spatially inhomogeneous 2D electronic system in the presence of an individual point, near the channel, on the electron density profile with an integer magnetic filling factor are determined. The magnetocapacitance between the edges of the Corbino disk separated by an incompressible interlayer is found for cases of practical interest. It is shown that this magnetocapacitance contains direct information about the width of the integer strip.

Current–voltage characteristic of a two-dimensional Corbino disk under the QHE conditions of quantum Hall effect

A theory of current–voltage characteristic (IVC) is proposed for a gated Corbino disk with a 2D spinless electron system and magnetic filling factors close to an integral value. The described results systematically include the features of the electrochemical potential of the 2D electron system in a magnetic field, which are responsible for sharp magnetocapacitance “dips” for integral values of the magnetic filling factor. The theory is used for qualitative interpretation of the observed weakly nonlinear peculiarities of IVC as well as for prediction of local details in the distribution of electron density and electric potential in a current-carrying Corbino disc. Corresponding measurements can be made, for instance, by using the linear electrooptical effect.

Minimum magnetocapacitance of a screened two-dimensional electron gas

A theory for the magnetocapacitance of a partially screened two-dimensional (2D) electron gas is proposed. The model investigated is sensitive to different types of screening in a 2D electron gas with an integer filling factor: the so-called conventional approach and the self-consistent approximation introduced in the present paper. The calculations point to the importance of the self-consistent treatment of the magnetocapacitance of a 2D electron gas under the conditions of an integer filling factor. The final self-consistent results are qualitatively consistent with the available experimental data.