arXiv subjects

O. E. Raichev

Publications and source records attributed to O. E. Raichev.

45 records · Page 3Linked to original sources

arXiv2007

Coulomb blockade of field emission from nanoscale conductors

Theoretical description of the field emission of electrons from nanoscale objects weakly coupled to the cathode is presented. It is shown that the field- emission current increases in a step-like fashion due to single-electron charging which leads to abrupt changes of the effective electric field responsible for the field emission. A detailed consideration of the current-voltage characteristics is carried out for a nanocluster modelled by a metallic spherical particle in the close vicinity of the cathode and for a cylindrical silicon nanowire grown on the cathode surface.

cond-mat.mes-hall↗

arXiv2006

Transient magnetoconductivity of photoexcited electrons

Transient magnetotransport of two-dimensional electrons with partially-inverted distribution excited by an ultrashort optical pulse is studied theoretically. The time-dependent photoconductivity is calculated for GaAs-based quantum wells by taking into account the relaxation of electron distribution caused by non-elastic electron-phonon interaction and the retardation of the response due to momentum relaxation and due to a finite capacitance of the sample. We predict large-amplitude transient oscillations of the current density and Hall field (Hall oscillations) with frequencies corresponding to magnetoplasmon range, which are initiated by the instability owing to the absolute negative conductivity effect.

cond-mat.mtrl-sci↗

arXiv2005

Transient response of photoexcited electrons: negative and oscillating current

Time-dependent current of the electrons excited in the conduction band after ultrafast interband photogeneration is studied theoretically. The transient photocurrent is calculated for the nonlinear regime of response to a stationary electric field. The response demonstrates transient absolute negative conductivity when the electrons are excited slightly below the optical phonon energy, while the periodic oscillations of the electric current appear after formation of the streaming distribution. The quenching of these peculiarities by the elastic scattering of electrons is also considered.

cond-mat.mtrl-sci↗

arXiv2000

Electron transport in Coulomb- and tunnel-coupled one-dimensional systems

We develop a linear theory of electron transport for a system of two identical quantum wires in a wide range of the wire length L, unifying both the ballistic and diffusive transport regimes. The microscopic model, involving the interaction of electrons with each other and with bulk acoustical phonons allows a reduction of the quantum kinetic equation to a set of coupled equations for the local chemical potentials for forward- and backward-moving electrons in the wires. As an application of the general solution of these equations, we consider different kinds of electrical contacts to the double-wire system and calculate the direct resistance, the transresistance, in the presence of tunneling and Coulomb drag, and the tunneling resistance. If L is smaller than the backscattering length l_P, both the tunneling and the drag lead to a negative transresistance, while in the diffusive regime (L >>l_P) the tunneling opposes the drag and leads to a positive transresistance. If L is smaller than the phase-breaking length, the tunneling leads to interference oscillations of the resistances that are damped exponentially with L.

cond-mat.mes-hall↗

arXiv2000

Ballistic electron transport in stubbed quantum waveguides: experiment and theory

We present results of experimental and theoretical investigations of electron transport through stub-shaped waveguides or electron stub tuners (ESTs) in the ballistic regime. Measurements of the conductance G as a function of voltages, applied to different gates V_i (i=bottom, top, and side) of the device, show oscillations in the region of the first quantized plateau which we attribute to reflection resonances. The oscillations are rather regular and almost periodic when the height h of the EST cavity is small compared to its width. When h is increased, the oscillations become less regular and broad depressions in G appear. A theoretical analysis, which accounts for the electrostatic potential formed by the gates in the cavity region, and a numerical computation of the transmission probabilities successfully explains the experimental observations. An important finding for real devices, defined by surface Schottky gates, is that the resonance nima result from size quantization along the transport direction of the EST.

cond-mat.mes-hall↗

arXiv1999

Coulomb Drag Between Parallel Ballistic Quantum Wires

The Coulomb drag between parallel, {\it ballistic} quantum wires is studied theoretically in the presence of a perpendicular magnetic field B. The transresistance R_D shows peaks as a function of the Fermi level and splitting energy between the 1D subbands of the wires. The sharpest peaks appear when the Fermi level crosses the subband extrema so that the Fermi momenta are small. Two other kinds of peaks appear when either {\it intra}- or {\it inter}-subband transitions of electrons have maximum probability; the {\it intra}-subband transitions correspond to a small splitting energy. R_D depends on the field B in a nonmonotonic fashion: it decreases with B, as a result of the suppression of backscattering, and increases sharply when the Fermi level approaches the subband bottoms and the suppression is outbalanced by the increase of the Coulomb matrix elements and of the density of states.

cond-mat.mes-hall↗

arXiv1999

Weak-localization corrections to the conductivity of double quantum wells

The weak-localization contribution δσ(B) to the conductivity of a tunnel-coupled double-layer electron system is evaluated and its behavior in weak magnetic fields B perpendicular or parallel to the layers is examined. In a perpendicular field B, δσ(B) increases and remains dependent on tunneling as long as the magnetic field is smaller than \hbar/e D τ_t, where D is the in-plane diffusion coefficient and τ_t the interlayer tunneling time. If τ_t is smaller than the inelastic scattering time, a parallel magnetic field also leads to a considerable increase of the concuctivity starting with a B**2 law and saturating at fields higher than \hbar/e Z (D τ_t)**(1/2), where Z is the interlayer distance. In the limit of coherent tunneling, when τ_t is comparable to elastic scattering time, δσ(B) differs from that of a single-layer system due to ensuing modifications of the diffusion coefficient. A possibility to probe the weak-localization effect in double-layer systems by the dependence of the conductivity on the gate-controlled level splitting is discussed.

cond-mat.mes-hall↗

arXiv1999

Effects of Coulomb interaction and tunneling on electron transport in coupled one-dimensional systems: from ballistic to diffusive regime

A linear theory of electron transport is developed for a system of two ideal quantum wires, of length L, coupled by tunneling and Coulomb interaction. The interaction of electrons with acoustical phonons is included and the results are valid in both the ballistic and diffusive regime. In the {\it ballistic} regime, both tunneling and Coulomb drag lead to a {\it negative} transresistance R_{TR}, while in the {\it diffusive} regime the tunneling opposes the drag and leads to a {\it positive} R_{TR}. If L is smaller than the phase-breaking length, the tunneling leads to interference oscillations of the resistance that are damped exponentially with L.

cond-mat.mes-hall↗

arXiv1999

Energy spectrum, density of states and optical transitions in strongly biased narrow-gap quantum wells

We study theoretically the effect of an electric field on the electron states and far-infrared optical properties in narrow-gap lead salt quantum wells. The electron states are described by a two-band Hamiltonian. An application of a strong electric field across the well allows the control of the energy gap between the two-dimensional (2D) states in a wide range. A sufficiently strong electric field transforms the narrow-gap quantum well to a nearly gapless 2D system, whose electron energy spectrum is described by linear dispersion relations ε_σ (k) ~\pm (k-k_σ), where k_σ are the field-dependent 2D momenta corresponding to the minimum energy gaps for the states with spin numbers σ. Due to the field-induced shift of the 2D subband extrema away from k=0 the density of states has inverse-square-root divergencies at the edges. This property may result in a considerable increase of the magnitude of the optical absorption and in the efficiency of the electrooptical effect.

cond-mat.mes-hall↗