Publications (100)63.15 Total impact
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ABSTRACT: We have measured the longitudinal and Hall resistivities in the quantum Hall regime at magnetic fields B up to 9 T and temperatures \(T =(2.9\div 50)\) K for the HgCdTe/HgTe/HgCdTe heterostructure with a wide HgTe quantum well. The temperatureinduced transport at the resistivity minima corresponding to the quantum Hall plateaus has been studied within the concept of hopping conduction in a strongly localized electron system. An analysis of the variablerange hopping conductivity in the regions of the first and second quantum Hall plateaus provided an opportunity to determine the value and the magneticfield dependence of the localization length with the experimental estimation of the critical indices.  [Show abstract] [Hide abstract]
ABSTRACT: The magneticfield dependencies of the longitudinal and Hall resistance of the electrondoped compounds Nd$_{2x}$Ce$_x$CuO$_{4+\delta}$ in underdoped region with $x$=0.14 and with varying degrees of disorder ($\delta$) were investigated. It was established experimentally that the correlation between the longitudinal electrical resistivity and the Hall resistivity can be analyzed on the basis of scaling relationships: $\rho_{xy}$($B$)$\sim$ $\rho^{\beta}_{xx}$($B$). For the totality of the investigated singlecrystal films of Nd$_{2x}$Ce$_x$CuO$_{4+\delta}$/SrTiO$_3$ the universal value $\beta$=1.5 $\pm$0.4 is found. The observed feature in the electrondoped twodimensional systems can be associated both with a displaying of anisotropic $s$  wave or $d$wave pairing symmetry and with a rather strong pinning due to an essential degree of disorder in the samples under study.  [Show abstract] [Hide abstract]
ABSTRACT: The longitudinal and Hall magnetoresistances of HgTe/HgCdTe heterostructures with an inverted energy spectrum (the HgTe quantum well width is d = 20.3 nm) are measured in the quantumHalleffect regime at T = 250 K in magnetic fields up to B = 9 T. Analysis of the temperature dependences of conductivity in the transition region between the first and second plateaus of the quantum Hall effect shows the feasibility of the scaling regime for a plateauplateau quantum phase transition in 2Dstructures on the basis of mercury telluride. 
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ABSTRACT: The longitudinal ρxx (B,T) and Hall ρxy (B, T) resistivities in the quantum Hall effect (QHE) regime for nInGaAs/GaAs nanostructures with single quantum wells are investigated at B = 012 T and T = 0.44.2 K, before and after IR illumination. The temperature dependences of QHE plateautoplateau transition width are analyzed by using the twoparameter scaling theory.  [Show abstract] [Hide abstract]
ABSTRACT: The dependences of the longitudinal and Hall resistances on a magnetic field in the integer quantum Hall effect regime in nInGaAs/GaAs heterostructures with a double quantum well are measured in the range of magnetic fields B = 016 T and temperatures T = 0.054.2 K, before and after infrared illumination. Analysis of the temperature dependence of the width of transitions between plateaus of the quantum Hall effect is performed in the scope of the scaling hypothesis allowing for electronelectron interaction effects.  [Show abstract] [Hide abstract]
ABSTRACT: The longitudinal ρ xx (B,T) and Hall ρ xy (B,T) magnetoresistances in nInGaAs/GaAs heterostructures with a single quantum well are studied experimentally before and after IR illumination in the quantum Hall regime in magnetic fields B = 0–12 T and at temperatures T = 0.4–4.2 K. The temperature dependence of the width of quantum Hall plateauplateau transitions is analyzed in terms of a twoparameter scaling theory.  [Show abstract] [Hide abstract]
ABSTRACT: We present the investigation results of the inplane \{rho}(T) resistivity tensor at the temperature range 0.440 K in magnetic fields up to 90kOe (Hc, Jab) for electrondoped Nd{2x}Ce{x}CuO{4+{\delta}} with different degree of disorder near antiferromagnetic  superconducting phase boundary. We have experimentally found that for optimally doped compound both the upper critical field slope and the critical temperature decrease with increasing of the disorder parameter (dwave pairing) while in the case of the underdoped system the critical temperature remains constant and (dHc2/dT)Tc increases with increasing of the disorder (swave pairing). These features suggest a possible implementation of the complex mixture state as the (s+id)pairing.  [Show abstract] [Hide abstract]
ABSTRACT: Results from studying the temperature dependence of resistivity of singlecrystal films of Nd1.86Ce0.14CuO4 (underdoped region) in magnetic fields of up to 90 kOe in the temperature range of 1.8–40 K are presented. The temperature dependence of the upper critical field obtained via the resistive method is analyzed using the impurity superconductor model with two types of carriers.  [Show abstract] [Hide abstract]
ABSTRACT: Investigations have been performed on the magneticfield dependences of the longitudinal and Hall resistivity of the electrondoped Nd2 − x Cex CuO4+δ system with an optimum content of cerium (x = 0.15) and different degree of the nonstoichiometric disorder in magnetic fields of up to 8 T (B ‖ c; J ‖ ab) in a temperature range of 0.4–4.2 K. The observed anomalous dependences of the Hall coefficient R(B) along with the dependences of the electrical resistivity ρ(B) have been interpreted based on the DrudeLorentz model in the case of the normal state and in the BardeenStephen model in the mixed state modified with allowance for the coexistence of two types of charge carriers with the opposite charge signs (electrons and holes). 
Article: Scaling in the Quantum Hall Regime for a Double Quantum Well Nanostructure in High Magnetic Field
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ABSTRACT: The longitudinal ρxx(B) and Hall ρxy(B) magnetoresistances are investigated in the integer quantum Hall effect regime in nInGaAs/GaAs double quantum well nanostructures in the magnetic fields B up to 16 T at temperatures T = (0.054.2) K before and after IR illumination. The analysis of the quantum Hall effect plateauplateau transitions based on the scaling hypothesis with regard to electronelectron interaction was carried out.  [Show abstract] [Hide abstract]
ABSTRACT: Using the resistivity method it was found that temperature dependence of the upper critical field for underdoped Nd1.86Ce0.14CuO4+δ have an anomalous upward curvature of Hc2(T) dependence and can be consistently explained by the twoband/twogap model of a dirty superconductor. Near antiferromagneticsuperconducting phase boundary the critical temperature remains constant with the change of the disorder parameter and the slope of Bc2 increases with increasing of the disorder parameter. This behavior is completely different from dependencies for pure superconducting phase at optimal doping region. This difference may indicate the change of the type of the paring: from the predominance of the anisotropic swave component (may be due to unstable competition between antiferromagnetic (AF) and superconducting (SC) regions) in underdoped (x=0.14) region to the prevalence of dwave part in optimal doped regions (x=0.15) because of residual spin fluctuations.  [Show abstract] [Hide abstract]
ABSTRACT: The longitudinal ρxx (B) and Hall ρxy (B) magnetoresistances are investigated experimentally in the integer quantum Hall effect (QHE) regime in nInGaAs/GaAs double quantum well nanostructures in the range of magnetic fields B = (0–16) T and temperatures T = (0.05–70) K before and after IR illumination. The results are evaluated within the scaling hypothesis with regard to electronelectron interaction. 
Article: Upper critical field in electrondoped cuprate superconductor Nd2−xCexCuO4+δ: Twogap model
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ABSTRACT: We present resistivity measurements of the upper critical field (Hc2) phase diagram as a function of temperature (T) for Nd1.85Ce0.15CuO4+δ/SrTiO3 single crystal films with different degree of disorder (δ) in magnetic fields up to 90 kOe at temperatures down to 0.4 K. The data are well described by a twoband/twogap model for a superconductor in the dirty limit.  [Show abstract] [Hide abstract]
ABSTRACT: Temperature and magneticfield dependences of longitudinal ρxx(B,T) and Hall ρxy(B,T) resistivities of nInxGa1xAs/GaAs nanostructures with single and double quantum wells are investigated in the quantum Hall effect (QHE) regime at B = 016 T and T = = 0.0570 K, before and after IR illumination. The temperature dependence of the QHE plateautoplateau transition width are analyzed and information about temperature dependences of the width of delocalized state stripes in the center of Landau subbands is obtained.  [Show abstract] [Hide abstract]
ABSTRACT: We present resistivity measurements of the upper critical field (H$_{c2}$) phase diagram as a function of temperature (T) for Nd$_{1.85}$Ce$_{0.15}$CuO$_{4+\delta}$/SrTiO$_3$ single crystal films with different degree of disorder ($\delta$) in magnetic fields up to 90 kOe at temperatures down to 0.4 K. The data are well described by a twoband/twogap model for a superconductor in the dirty limit.  [Show abstract] [Hide abstract]
ABSTRACT: Transport properties of Nd2−xCexCuO4+δ/SrTiO3 single crystal films (B‖c,J‖abB‖c,J‖ab) are investigated in magnetic fields B up to 9T at T = (0.4–4.2) K. An analysis of normal state (at B>Bc2B>Bc2) Hall coefficient RHn dependence on Ce doping takes us to a conclusion about the existence both of electronlike and holelike contributions to transport in nominally electrondoped system. In accordance with RHn(x) analysis an anomalous sign reversal of Hall effect in mixed state at B<Bc2B<Bc2 may be ascribed to a fluxflow regime for two types of carriers with opposite charges.  [Show abstract] [Hide abstract]
ABSTRACT: We report on the results of analyzing the temperature dependences of the resistivity of the Nd2 − x Cex CuO4 + δ electronic superconductor with x = 0.14 (underdoped range), x = 0.15 (optimal doping), and x = 0.18 (overdoped range) and with various degrees of annealing in an oxygenfree atmosphere in magnetic fields up to H = 90 kOe (H ‖ c, J ‖ ab) in the temperature range T = (0.4–300) K. It is shown that the observed differences in the dependences of the slope of the upper critical field $(dH_{c2} /dT)_{T_c } $ on the degree of disorder in the Nd2 − x Cex CuO4 + δ system upon a change in the cerium doping level indicate a change in the symmetry of dtype pairing to anisotropic s pairing.  [Show abstract] [Hide abstract]
ABSTRACT: The resistivity (ρ) of low mobility dilute 2D electron gas in an nInGaAs/GaAs double quantum well (DQW) exhibits the monotonic "insulatinglike" temperature dependence (dρ/dT < 0) at T = 1.8–70 K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kBTτ/ħ > 0.1–3.5) for our samples, and the electron density is on an "insulating" side of the socalled B = 0 2D metal–insulator transition. We show that the observed features of localization and Landau quantization in a vicinity of the low magneticfieldinduced insulator–quantum Hall liquid transition is due to the σxy(T) anomalous Tdependence.  [Show abstract] [Hide abstract]
ABSTRACT: The inplane resistivity, Hall effect (T = 77 K) and SCtransition for some Nd1.85Ce0.15CuO4+δ single crystal films are investigated at different nonstoichiometric disorder (δ). It is shown that with increasing of δ the Hallcoefficient for the most of the samples differs no more than twice but the normal state resistivity increases by a factor of five. SCtransition temperature decreases with essential broadening of the transition region. The observed evolution from homogeneous metallic (and superconducting) Nd1.85Ce0.15CuO4+δ system to inhomogeneous dielectric one is described as Andersontype disorderinduced transition in a twodimensional electron system.
Publication Stats
225  Citations  
63.15  Total Impact Points  
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Institutions

19972015

Russian Academy of Sciences
 Institute of Metal Physics
Moskva, Moscow, Russia


19962014

Institute of Metal Physics
Sverolovsk, Sverdlovsk, Russia


2004

University of Amsterdam
Amsterdamo, North Holland, Netherlands
