G. M. Gusev

Transport in disordered two-dimensional topological insulators

We study experimentally the transport properties of inverted semiconductor HgTe-based quantum well, which is related to the two-dimensional topological insulator, in diffusive transport regime. nWe perform nonlocal electrical measurements in the absence of the magnetic field and observe large signal due to the edge states. It demonstrates, that the edge states can propagate over long distance 1 mm, and, therefore, there is no difference between local and non local electrical measurements in topological insulator. In the presence of the in-plane magnetic field we find strong decrease of the local resistance and complete suppression of the nonlocal resistance. We attribute this observation to the transition between topological insulator and bulk metal induced by the in-plane magnetic field.

Large positive magnetoresistance in a high-mobility two-dimensional electron gas: Interplay of short- and long-range disorder

We have observed a large positive quasiclassical magnetoresistance (MR) in a high mobility two-dimensional electron gas in an

Magnetoresistance oscillations in multilayer systems: Triple quantum wells

mathrm{AlGaAs}∕mathrm{GaAs}

Sensitivity of the universal conductance fluctuations in a GaAs microstructure to the state of a single scatterer

heterostructure. The magnetoresistance is nonsaturating and increases with magnetic field as

Macroscopic transverse drift of long current-induced spin coherence in two-dimensional electron gases

ensuremath{Delta}{ensuremath{rho}}_{xx}ensuremath{sim}{B}^{ensuremath{alpha}}phantom{rule{0.3em}{0ex}}(ensuremath{alpha}=0.9ensuremath{-}1.2)

Large anisotropic spin relaxation time of exciton bound to donor states in triple quantum wells

. In antidot lattices a nonmonotonic MR is observed. We show that in both cases this MR can be qualitatively described in terms of the theory recently advanced by Polyakov et al. [Phys. Rev. B 64, 205306 (2001)]. Their prediction is that the behavior we observe may be the consequence of a concurrent existence of short- and long-range scattering potentials.

Emergent fractional quantum Hall effect at even denominator ν = 3/2 in a triple quantum well in tilted magnetic fields

Magnetoresistance of two-dimensional electron systems with several occupied subbands oscillates owing to periodic modulation of the probability of intersubband transitions by the quantizing magnetic field. In addition to previous investigations of these magnetointersubband (MIS) oscillations in two-subband systems, we report on both experimental and theoretical studies of such a phenomenon in three-subband systems realized in triple quantum wells. We show that the presence of more than two subbands leads to a qualitatively different MIS oscillation picture, described as a superposition of several oscillating contributions. Under a continuous microwave irradiation, the magnetoresistance of triple-well systems exhibits an interference of MIS oscillations and microwave-induced resistance oscillations. The theory explaining these phenomena is presented in the general form, valid for an arbitrary number of subbands. A comparison of theory and experiment allows us to extract temperature dependence of quantum lifetime of electrons and to confirm the applicability of the inelastic mechanism of microwave photoresistance for the description of magnetotransport in multilayer systems.

Microwave-Induced Magneto-Oscillations and Signatures of Zero-Resistance States in Phonon-Drag Voltage in Two-Dimensional Electron Systems.

Discrete multilevel spontaneous resistance fluctuations have been observed in a microstructure fabricated on a delta -doped GaAs layer base. The authors suggest that this behaviour of the resistance is caused by random discrete changes of states of individual impurity atoms. They have been able to observe the influence of the change of the state of a single scatterer on the universal conductance fluctuations. Comparison with theory is made.

Gate control of the spin mobility through the modification of the spin-orbit interaction in two-dimensional systems

We imaged the transport of a current-induced spin coherence in a two-dimensional electron gas confined in a triple quantum well. Nonlocal Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization, revealed a large spatial variation of the electron g-factor and the efficient generation of a current-controlled spin-orbit field in a macroscopic Hall bar device. We observed coherence times in the nanoseconds range transported beyond half-millimeter distances in a direction transverse to the applied electric field. The measured long spin transport length can be explained by two material properties: large mean free path for charge diffusion in clean systems, and enhanced spin-orbit coefficients in the triple well.

Magnetocapacitance oscillations and thermoelectric effect in a two-dimensional electron gas irradiated by microwaves

We have studied the spin dynamics of a dense two-dimensional electron gas confined in a GaAs/AlGaAs triple quantum well by using time-resolved Kerr rotation and resonant spin amplification. Strong anisotropy of the spin relaxation time up to a factor of 10 was found between the electron spins oriented in-plane and out-of-plane when the excitation energy is tuned to an exciton bound to neutral donor transition. We model this anisotropy using an internal magnetic field and the inhomogeneity of the electron g-factor. The data analysis allows us to determine the direction and magnitude of this internal field in the range of a few mT for our studied structure, which decreases with the sample temperature and optical power. The dependence of the anisotropic spin relaxation was directly measured as a function of several experimental parameters: excitation wavelength, sample temperature, pump-probe time delay, and pump power.