Low-temperature dependences of the amplitude of magneto-intersubband resistance oscillations ( $$\Delta {{R}_{{{\text{MISO}}}}}$$ ) on the magnetic field $$B < 2$$ T are studied in single GaAs quantum wells with the width ( $${{d}_{{{\text{SQW}}}}}$$ ) from 22 to 46 nm and two occupied quantum confinement subbands $${{E}_{1}}$$ and $${{E}_{2}}$$ . It is established that additional damping appears in dependences of $$\Delta {{R}_{{{\text{MISO}}}}}$$ on 1/ $$B$$ in the studied quantum wells, which is explained by the effect of large-scale fluctuations of the intersubband splitting $${{\Delta }_{{12}}} = {{E}_{2}} - {{E}_{1}}$$ on the amplitude of oscillations $$\Delta {{R}_{{{\text{MISO}}}}}$$ . It is found that the suppression of oscillations $$\Delta {{R}_{{{\text{MISO}}}}}$$ with the increase in 1/ $$B$$ is more efficient in “narrow” quantum wells. This experimental fact makes it possible to suppose that the main origin of fluctuations of $${{\Delta }_{{12}}}$$ in the studied narrow quantum wells is large-scale fluctuations of the well width $${{d}_{{{\text{SQW}}}}}$$ . An expression taking into account the role of large-scale fluctuations of $${{\Delta }_{{12}}}$$ in the damping of $$\Delta {{R}_{{{\text{MISO}}}}}$$ is obtained. The comparison of theory and experiment has made it possible to determine the average amplitude of fluctuations of the intersubband splitting in the studied GaAs quantum wells.

Shubnikov de Haas resistance oscillations of highly mobile two dimensional helical electrons propagating on a conducting surface of strained HgTe 3D topological insulator are studied in magnetic fields B tilted by angle θ from the normal to the conducting layer. Strong decrease of oscillation amplitude A is observed with the tilt: A∼exp( - ξ/cos(θ)) , where ξ is a constant. Evolution of the oscillations with temperature T shows that the parameter ξ contains two terms: ξ=ξ_1+ξ_2T . The temperature independent term, ξ_1 , signals possible reduction of electron mean free path l_q and/or enhancement of in-homogeneous broadening of the oscillations in magnetic field B . The temperature dependent term, ξ_2T , indicates increase of the reciprocal velocity of 2D helical electrons: δ (v_F^-1)∼ B suggesting modification of the electron spectrum in magnetic fields. Results are found in good agreement with proposed phenomenological model.

The effect of microwave radiation on low-temperature electron magnetotransport in a square antidot lattice with a period of d ≈ 0.8 µm based on a GaAs quantum well with two occupied energy subbands E1 and E2 is investigated. It is shown that, owing to a significant difference between the electron densities in the subbands, commensurability oscillations of the resistance in the investigated antidot lattice are observed only for the first subband. It is found that microwave irradiation under the cyclotron resonance condition results in the formation of resistance oscillations periodic in the inverse magnetic field in the region of the main commensurability peak. It is established that the period of these oscillations corresponds to the period of magneto-intersubband oscillations. The observed effect is explained by the increase in the rate of intersubband scattering caused by the difference between the electron heating in the subbands E1 and E2.

Electron transport in single GaAs quantum wells of widths from 22 to 46 nm with two populated quantum-confinement subbands ES and EAS is investigated at a temperature of T = 4.2 K in tilted magnetic fields B < 2 T. The angle α between the applied magnetic field and the normal to the plane of the structure under study is varied from 0° to 90°. In a perpendicular magnetic field (α = 0), magnetointersubband oscillations with a period determined by the relation ΔSAS = EAS - ES = jħωc, where ωc is the cyclotron frequency and j is a positive integer, are observed in all investigated quantum wells. In tilted fields, the peaks of magnetointersubband oscillations are shifted toward higher fields B cos α. This shift is explained by an increase in the energy splitting ΔSAS with increasing component B sin α. In 46- and 36-nm-wide quantum wells, beats of magnetointersubband oscillations are observed at angles α > 72° and α > 85°, respectively. The origin of this unexpected behavior of magnetointersubband oscillations in tilted magnetic fields is discussed.

Shubnikov de Haas resistance oscillations of highly mobile two dimensional helical electrons propagating on a conducting surface of strained HgTe 3D topological insulator are studied in magnetic fields B tilted by angle $\theta$ from the normal to the conducting layer. Strong decrease of oscillation amplitude A is observed with the tilt: $A \sim \exp(-\xi/cos(\theta))$, where $\xi$ is a constant. Evolution of the oscillations with temperature T shows that the parameter $\xi$ contains two terms: $\xi=\xi_1+\xi_2 T$. The temperature independent term, $\xi_1$, describes reduction of electron mean free path in magnetic field B pointing toward suppression of the topological protection of the electron states against impurity scattering. The temperature dependent term, $\xi_2 T$, indicates increase of the reciprocal velocity of 2D helical electrons suggesting modification of the electron spectrum in magnetic fields.

In this paper we report on an explosive disintegration of metallic 3D samples with built-in nanoscaled hierarchical order under electron beam irradiation in a transmission electron microscope. The objects of our investigation are novel 3D mesostructures containing either FeNi3 intermetallic nanowires, or silver wafers of nanoscale thickness, or Pb–In nanorods. These structures were fabricated via a self-organization of metallic nanowires growing on templates during the pulsed electro-deposition process. The disintegration of 3D mesostructures yields an array of 2–50 nm metallic crystalline nanoparticles scattered on a holding substrate in the vicinity of the contact of the electron beam with samples. Direct atomic resolution images made in-situ reveal the monocrystalline structure of the nanoparticles. The observed rapid disintegration of 3D mesostructures in the electron beam is related to the internal energy significantly enhanced in the nanostructured samples. Possible applications of the phenomenon are discussed.

Nonlinear magnetotransport in a two-dimensional electron gas in one-dimensional lateral lattices fabricated from a selectively doped GaAs/AlAs heterostructure is investigated. One-dimensional potential modulation is imposed on the two-dimensional electron gas by means of a set of metal strips formed on the planar surface of Hall bars. The dependences of the differential resistance r xx on the magnetic field B < 0.5 T are studied at a temperature T = 1.6 K in lattices with a period of a ≈ 200nm. It is shown that periodic oscillations in r xx (1/ B ) occur in such lattices under the action of a current-induced Hall field due to Zener tunneling between Landau levels. Interference is found between Zener oscillations and commensurability oscillations of r xx in two-dimensional electron systems with one-dimensional periodic modulation. The experimental results are qualitatively explained by the role of Landau bands in nonlinear transport at large filling factors.

We report that volumetric mesoporous structures obtained via self-organization of Pd-Ni nanowires interact actively with low temperature non-equilibrium oxygen plasma. This interaction leads to strong red incandescence of the composite nanostrucutures. After the plasma-chemical treatment, the X-ray diffraction pattern reveals presence of nanocrystalline nickel (II) oxide phase on surface of the samples. Measurements of electromagnetic response indicate that the samples exposed to oxygen plasma retain metallic type conductivity which is similar to the pristine Pd-Ni samples. Thus our studies indicate that the plasma-chemical treatment yields novel composite 3D hierarchical structures with a highly conductive skeleton of Pd-Ni nanowires covered by a thin nickel (II) oxide semiconducting layer of large surface area. These structures are attractive for applications. (C) 2017 Elsevier B.V. All rights reserved.

The effect of electric field E on the conductance of highly mobile two-dimensional electrons placed in crossed electric and quantizing magnetic fields has been investigated. Electric field induced oscillations of differential conductivity and electronic state with zero-differential conductance of two-dimensional electrons are observed in GaAs quantum wells in Corbino geometry. The oscillations are periodic in the square of the inverse magnetic field, and occur in Corbino rings with a width which is much smaller than the rings' radius. The conductance oscillations are described by Zener tunneling between Landau orbits in the absence of the Hall electric field. The zero-differential conductance state occurs above a critical electric field E>Eth at low temperatures, and is accompanied by an abrupt dip in the differential conductance. The proposed model considers a local instability of the electric field as the origin of the observed phenomenon.

The nonlinear magnetotransport of a two-dimensional (2D) electron gas in one-dimensional lateral superlattices based on a selectively doped GaAs/AlAs heterostructure is studied. The one-dimensional potential modulation of the 2D electron gas is performed by means of a series of metallic strips formed on the surface of a heterostructure with the use of electron beam lithography and a lift-off process. The dependence of the differential resistance r xx on the magnetic field B < 1.5T in superlattices with the period a = 400 nm at a temperature of T = 4.2 K is investigated. It is found that electronic states with r xx ≈ 0 appear in one-dimensional lateral superlattices in crossed electric and magnetic fields. It is shown that states with r xx ≈ 0 in 2D electronic systems with one-dimensional periodic modulation arise at the minima of commensurability oscillations of the magnetoresistance.

In this article we report about active interaction of volumetric mesoscopic structures composed of PdNi alloy nanowires with low temperature nonequilibrium oxygen plasma. Object of our study is fine 3D meso-structures, which were fabricated via a self-organization of nanowires growing during the electrodeposition of metals on a template.

The influence of microwave radiation on the low-temperature magnetotransport of two-dimensional electrons in a one-dimensional lateral superlattice fabricated on the basis of a selectively doped GaAs/AlAs heterojunction has been investigated. It has been found that the resistance of the two-dimensional electron gas in this superlattice changes under the action of microwave radiation more substantially at the minima of commensurate oscillations than at the maxima. The experimental data demonstrate “interference” of classical commensurate magnetoresistance oscillations and quantum microwave-induced oscillations.

The architecture of novel metallic mesostructures obtained via self-organization of growing nanowires has been investigated. Seashell-, fungus- and lotus leaf-shaped structures are reproducibly formed by programmable pulse current electrodeposition on porous membranes. The obtained samples were several millimeters in size. SEM investigation has revealed that the frame of the metallic “seashell” presents a hierarchical system with elements of fractal self-similarity at the nano- and micro-levels. The frame is a volumetric multilayer net with conical bundles of nanowires as building blocks. Pd–Ni nanowires have V-like branches and periodic bulges (“beads”). TEM study showed that nanowires consist of nanocrystallites dispersed in an amorphous matrix. Their sizes range from 4 to 15nm. Local inhomogeneity of Pd–Ni solid solution was observed. In perspective, the proposed technique can be used as a 3D printer for the purposeful synthesis of novel materials with complex quantum nano-architecture.

Nonlinear magnetotransport of two-dimensional electrons in modulation-doped GaAs/AlAs heterostructures with anisotropic mobility is investigated. The mobility attains its maximum and minimum values in the \(\left[ {1\bar 10} \right]\) and [110] directions, respectively. It is found that, upon an increase in the direct electrical current I dc though Hall bars oriented along the [110] direction, the transition of the two-dimensional system to the state with differential resistance r xx ≈ 0 in a magnetic field occurs at a lower value of I dc and is accompanied by a more pronounced “plunge” into the region of negative r xx values as compared to bars oriented along the \(\left[ {1\bar 10} \right]\) direction. The results are explained by the impact of mobility on the spectral diffusion of nonequilibrium charge carriers.

Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La2−xSrxCuO4 layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV∼γI3, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ/dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area ge−ph≈1 W/K cm2 at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

Low-temperature dependences of the transport relaxation time (τtr) and quantum lifetime (τq) on the density of the two-dimensional electron gas (n e ) in GaAs quantum wells with AlAs/GaAs lateral superlattice barriers have been studied. An exponential increase in the quantum lifetime with increasing electron density has been observed. It has been shown that the sharp increase in the quantum lifetime correlates with the appearance of X electrons in the AlAs/GaAs lateral superlattice barriers. It has been established that the ratio of the transport relaxation time to the quantum lifetime in the studied structures nonmonotonically depends on the density: the ratio τtr/τq first increases linearly with n e and then decreases. This behavior is not described by the existing theories.