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We apply a novel inductive coupling technique to study edge magnetoplasmons (EMP) in two-dimensional electron gases in the time domain. This technique is mostly appropriated for measurements on gated samples in the low-magnetic-field limit. We obtain time delay, amplitude, and broadening of the EMP as a function of the magnetic field.

In the ballistic regime, the metallic temperature dependence of the conductivity in a two-dimensional electron system in silicon is found to change non-monotonically with the degree of spin polarization. In particular, it fades away just before the onset of complete spin polarization but reappears again in the fully spin-polarized state, being, however, suppressed relative to the zero-field case. Analysis of the degree of the suppression allows one to distinguish between the screening and the interaction-based theories.

We experimentally study electron transport between edge states in the fractional quantum Hall effect regime. We find an anomalous increase of the transport across the 2/3 incompressible fractional stripe in comparison with theoretical predictions for the smooth edge potential profile. We interpret our results as a first experimental demonstration of the intrinsic structure of the incompressible stripes arising at the sample edge in the fractional quantum Hall effect regime., Comment: 5 pages, 5 figures included. Submitted to JETP Letters

We experimentally demonstrate, for the first time, formation of point-like topological defects in the edge state structure in the quantum Hall effect regime. By using of a selective population technique, we investigate equilibration processes between the edge states in bilayer electron structures with a high tunnelling rate between layers. Unexpected flattening of the I-V curves in perpendicular magnetic field at a specific filling factor combination and the recovery of the conventional nonlinear I-V characteristics in tilted fields give a strong evidence for the existence of topological defects., 4 pages, 3 figures included

We use a quasi-Corbino sample geometry with independent contacts to different edge states in the quantum Hall effect regime to investigate the edge energy spectrum of a bilayer electron system at total filling factor $\nu=2$. By analyzing non-linear $I-V$ curves in normal and tilted magnetic fields we conclude that the edge energy spectrum is in a close connection with the bulk one. At the bulk phase transition spin-singlet - canted antiferromagnetic phase $I-V$ curve becomes to be linear, indicating the disappearance or strong narrowing of the $\nu=1$ incompressible strip at the edge of the sample., Comment: 5 pages, 5 figures

Using an innovative combination of a quasi-Corbino sample geometry and the cross-gate technique, we have developed a method that enables us to separately contact single edge channels in the quantum Hall regime and investigate equilibration among them. Performing 4-point resistance measurements, we directly obtain information on the energetic and geometric structure of the edge region and the equilibration-length for current transport across the Landau- as well as the spin-gap. Based on an almost free choice in the number of participating edge channels and their interaction-length a systematic investigation of the parameter-space becomes possible., 8 pages, 7 figures

We study the plateaux of the integer quantum Hall resistance in a bilayer electron system in tilted magnetic fields. In a narrow range of tilt angles and at certain magnetic fields, the plateau level deviates appreciably from the quantized value with no dissipative transport emerging. A qualitative account of the effect is given in terms of decoupling of the edge states corresponding to different electron layers/Landau levels., Comment: 3 pages, 3 figures included

We employ magnetocapacitance measurements to study the spectrum of a double layer system with gate-voltage-tuned electron density distributions in tilted magnetic fields. For the dissipative state in normal magnetic fields at filling factor $\nu=3$ and 4, a parallel magnetic field component is found to give rise to opening a gap at the Fermi level. We account for the effect in terms of parallel-field-caused orthogonality breaking of the Landau wave functions with different quantum numbers for two subbands., Comment: 4 pages, 4 figures included, to appear in JETP Letters

We investigate the double-layer electron system in a parabolic quantum well at filling factor $\nu=2$ in a tilted magnetic field using capacitance spectroscopy. The competition between two ground states is found at the Zeeman splitting appreciably smaller than the symmetric-antisymmetric splitting. Although at the transition point the system breaks up into domains of the two competing states, the activation energy turns out to be finite, signaling the occurrence of a new insulator-insulator quantum phase transition. We interpret the obtained results in terms of a predicted canted antiferromagnetic phase., Comment: 4 pages, 3 figures included, accepted to PRL

We study the lateral tunneling through the gate-voltage-controlled barrier, which arises as a result of partial elimination of the donor layer of a heterostructure along a fine strip using an atomic force microscope, between edge channels at the depletion-induced edges of a gated two-dimensional electron system. For a sufficiently high barrier a typical current-voltage characteristic is found to be strongly asymmetric and include, apart from a positive tunneling branch, the negative branch that corresponds to the current overflowing the barrier. We establish the barrier height depends linearly on both gate voltage and magnetic field and we describe the data in terms of electron tunneling between the outermost edge channels., Comment: 4 pages, 4 figures. Accepted to JETP Lett

We employ magnetocapacitance and far-infrared spectroscopy techniques to study the spectrum of the double-layer electron system in a parabolic quantum well with a narrow tunnel barrier in the center. For gate-bias-controlled asymmetric electron density distributions in this soft two-subband system we observe both individual subband gaps and double-layer gaps at integer filling factor $\ensuremath{\nu}.$ The bilayer gaps are shown to be either trivially common for two subbands or caused by the wave function reconstruction in growth direction as induced by intersubband electron transfer at a normal to the interface magnetic field. In the latter case the observed gaps at $\ensuremath{\nu}=1$ and $\ensuremath{\nu}=2$ are described within a simple model for the modified bilayer spectrum.

The zero bias anomaly (ZBA) of the tunnel conductivity are investigated in the Al/δ – GaAs tunnel structure with 2D electron concentration in δ-layer to be equal to 3.6*1012 cm−2. We find that the dip (ZBA) in the tunnel density of states near the Fermi level EF reveals logarithmic dependence on the energy e in the range kT < < /r. Here is the energy relative to Ef and r is the elastic relaxation time of 2D electrons. The depth of the ZBA is proportional to ln(T/T0) in the range T = 0.1 – 20 K. These results are in agreement with Aronov-Altshuler theory in which the correction to the 2D density of states is due to the effects of the electron-electron interaction in diffusion channel. The unusual behavior of the tunnel magnetoconductivity is observed.

Strong electron–electron interactions in dilute two-dimensional electron systems in silicon lead to Pauli spin susceptibility growing critically at low electron densities. This effect originates from renormalization of the effective mass rather than the g-factor. The relative mass enhancement is system and disorder independent, which suggests that it is determined by electron–electron interactions only.

Using a quasi-Corbino geometry to directly study electron transport between spin-split edge states under high imbalance conditions, we find a pronounced hysteresis in the I−V curves originating from dynamic nuclear polarization near the sample edge. Already in the simplest case of filling factor ν=2 we observe a complicated relaxation, depending on the sign of the electrochemical potential difference. The characteristic relaxation times are about 25 s and 200 s, which points to the presence of two different relaxation mechanisms. The two time constants are ascribed to the formation of a local nuclear polarization due to flip-flop processes and the diffusion of nuclear spins.