Renormalization of the contribution of the electron—electron interaction to the conductivity of two-dimensional electron systems

The contribution of the electron—electron interaction to the conductivity of the two-dimensional electron gas in an In_x Ga_1-x As single quantum well with different disorder strengths was experimentally studied. It is shown that the data are described well within the framework of the one-loop approximation of the renormalization group theory so long as the conductivity of the system remains higher than around 15e ²/μh.     

Percolation and the electron–electron interaction in an array of antidots

A square lattice of microcontacts with a period of 1 μm in a dense low-mobility two-dimensional electron gas is studied experimentally and numerically. At the variation of the gate voltage V _g , the conductivity of the array varies by five orders of magnitude in the temperature range T from 1.4 to 77 K in good agreement with the formula σ(V _g ) = (V _g ?V _g ^* (T))^β with β = 4. The saturation of σ(T) at low temperatures is absent because of the electron–electron interaction. A random-lattice model with a phenomenological potential in microcontacts reproduces the dependence σ(T, V _g ) and makes it possible to determine the fraction of microcontacts x(V _g , T) with conductances higher than σ. It is found that the dependence x(V _g ) is nonlinear and the critical exponent in the formula σ ∝ ? (x - 1/2) ^t in the range 1.3 < t(T, V _g ) < β.     

Bias-dependent bandwidth of the conductance in the presence of electron–phonon interaction

We study the electronic transport in the presence of electron–phonon interaction (EPI) for a molecular electronic device. Instead of mean field approximation (MFA), the related phonon correlation function is conducted with the Langreth theorem (LT). We present formal expressions for the bandwidth of the electron’s spectral function in the central region of the devices, such as quantum dot (QD), or single molecular transistor (SMT). Our results show that the out-tunneling rate depends on the energy, bias voltage and the phonon field. Besides, the predicted conductance map, behaving as a function of bias voltage and the gate voltage, gets blurred at the high bias voltage region. These EPI effects are consistent with the experimental observations in the EPI transport experiment.     

Characteristic features of the singlet–triplet mechanism of the electron spin polarization

Characteristic features of net chemically induced dynamic electron spin polarization (CIDEP) P _n in triplet–radical (TR) quenching are analyzed in detail within the framework of a general model that enables one to analyze CIDEP both numerically and analytically. This model also makes it possible to accurately describe the nonadiabatic transitions between the terms of the TR-pair spin Hamiltonian that lead to CIDEP generation. The proposed theory yields a simple analytical dependence of P _n on the parameters of the model. In particular, it is shown that, within a wide region of parameters, the dependence of P _n on the coefficient of relative TR diffusion D _r is described by a simple linear relation: \(P_n^{ - 1}\left( {{D_r}} \right) = {Q_0} + \overline {{q_n}} {D_r}\) (with Q ₀ and \({{q_n}}\) independent of D _r ). It is also demonstrated that the numerical and analytical results obtained are very useful in analysis of experimental data, as demonstrated by analyzing the experimental dependence of P _n on D _r .     

Is the Pauli exclusion principle the origin of electron localisation?

ABSTRACT

In this work, we inquire into the origins of the electron localisation as obtained from the information content of the same-spin pair density, γ^{σ, σ}(r₂∣r₁). To this end, we consider systems of non-interacting and interacting identical Fermions contained in two simple 1D potential models: (1) an infinite potential well and (2) the Kronig–Penney periodic potential. The interparticle interaction is considered through the Hartree–Fock approximation as well as the configuration interaction expansion. Morover, the electron localisation is described through the Kullback–Leibler divergence between γ^{σ, σ}(r₂∣r₁) and its associated marginal probability. The results show that, as long as the adopted method properly includes the Pauli principle, the electronic localisation depends only modestly on the interparticle interaction. In view of the latter, one may conclude that the Pauli principle is the main responsible for the electron localisation.     

Probing the onset of strong localization and electron–electron interactions with the presence of a direct insulator–quantum Hall transition

We have performed low-temperature transport measurements on a disordered two-dimensional electron system (2DES). Features of the strong localization leading to the quantum Hall effect are observed after the 2DES undergoes a direct insulator–quantum Hall transition on increasing the perpendicular magnetic field. However, such a transition does not correspond to the onset of strong localization. The temperature dependences of the Hall resistivity and Hall conductivity reveal the importance of the electron–electron interaction effects for the observed transition in our study.     

Features of the formation of electron bunches upon the development of generation in multiwave Čerenkov devices

The dynamics of electron bunch formation are analyzed using data obtained by means of numerical simulation. It is shown that upon the development of microwave generation, electron bunches start to form in a relativistic flow in the first section of the electrodynamic structure. At the entrance to the second section, a complex structure of electron distribution over a longitudinal pulse is observed inside the bunch in the stationary mode of generation. It is concluded that the duration of a microwave radiation pulse can be increased by optimizing the length of the first section of the generator.     

Theoretical study of the intensity of chemically induce dynamic electron polarization of radical-triplet pairs

Considering the interaction between encited triplet molecule and cloublet radical,based on the second-order perturbation theroy and the motion equation of density matrix,the polarzation intersity of RTPM were theoretically calculated with the overpopulated doublet spin states and quartet spin states of radical0triplet paris as initial conditions the radical result from the zero-field-splitting(zfs)and the multiplet A/E and E/A polarization result from hyperfine (hf) interactions of the triplet molcule,The hyperfine ralated A A/E or E E/A CIDEP on the radical were the overpopulation of the net abscrptive or emissive polarization and multiple A/E or E/A polarization.     

Modeling of variations of the peak F2 layer electron density and total electron content during the recovery period after the magnetic storm of April 15–20, 2002

The results of numerical modeling by using the global upper atmosphere model of the Earth (UAM) for reproducing the peak F2 layer electron density (N _m F2) and total electron content (TEC) during recovery period after the magnetic storm of the April 15–20, 2002 are discussed. According to the simulations, the time it takes to reach a stationary regime of N _m F2 and TEC diurnal variations is 24 hours, much shorter then the plasmasphere refilling time. The results are compared with the predictions of the IRI-2007 empirical model and GPS data on the TEC and found in good quantitative agreement for the latitudinal variations of N _m F2 and TEC for daytime conditions in the southern hemisphere. The worst agreement occurs in the region of the main ionospheric trough.     

On the phase diagram of a two-dimensional electron–hole system

The phase diagram for a system of spatially separated electrons and holes in coupled quantum wells or graphene double layers is studied in the framework of a BCS-like mean-field approach and a Landau expansion in terms of the pairing order parameter. We find a second order transition between an electron–hole plasma and a BCS phase, as well as a first-order transition between the BCS phase and a bosonic Mott phase of tightly bound electron–hole pairs without phase coherence. The electron–hole plasma exists at low and at high densities for weak interaction, the BCS phase at moderate density and the Mott phase at high density and strong interaction.     

Axially magnetized electron–positron and electron plasma competition on the self focusing of intense laser beam

The spot-size evolution of circularly polarized intense laser beam propagating through the axially magnetized electron–positron (EP) and electron plasmas is discussed, in mildly relativistic and weakly non-linear (a² ? 1) regime. The non-linear current density source terms are obtained by making used of the perturbative technique. The variational principle approach method is applied to the solution of the non-linear Schrodinger wave equation. It is shown that the laser beam spot size decreases for the left and increases for the right handed polarized beams with increasing the external magnetic field, owing to the beam passages inside the electron plasma. Furthermore, it is revealed that the self focusing property strongly enhanced in the EP plasma in comparison to the electron plasma. Moreover, self focusing of linearly polarized laser beam is investigated for EP plasma by superposition of the right and left circularly polarized beams.     

Thermoelectric properties of the interacting two dimensional electron gas in the diffusion regime?

We demonstrate that kinetic coefficients related to thermoelectric properties of the two dimensional electron gas in the diffusive regime are strongly influenced by electron-electron interaction. As an example we consider the thermoelectric coefficients of the diluted two-dimensional electron gas in Si(100) MOSFET’s in the presence of charged-impurity scattering. We find that the screening anomaly at q = 2k _F, also responsible for Friedel oscillations, leads at low electron densities to a large change in the thermoelectric coefficient for the thermopower.     

To the question of electron angular distribution at Μ-meson decay

The paper describes the measurement of the angular distribution of electrons at the decay of-mesons in a longitudinal magnetic field. The results of measurement indicate that electrons are emitted with preference not only in the direction parallel to the spin orientation of -meson but also in the antiparallel direction in disagreement with the angular distribution predicted by theory.

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The authors thank N. V. Rabin for irradiating the nuclear emulsions, Prof. Dr. V. Petrílka and M. Suk for mediating relations with the Joint Institute of Nuclear Research in Dubna and Dr. J. Pernegr for valuable discussions and remarks. Thanks also go to H. Koutová and H. Slámová for carefully scanning the nuclear emulsions.     

Suppression of electron correlations in the superconducting alloys of Rh17−xIrxS15

We have studied the effect of Iridium doping (Rh_17?xIr_xS₁₅) in the rhodium sites of the strongly correlated superconductor Rh₁₇S₁₅. Even at low levels of doping (x = 1 and 2) we see a drastic change in the superconducting properties as compared to those of the undoped system. We deduce that there is a reduction in the density of states at the Fermi level from reduced Pauli susceptibility and Sommerfeld coefficient in the doped samples. Moreover, the second magnetization peak in the isothermal magnetization scan (‘fishtail’) which was very prominent in the magnetization data of the undoped crystal is suppressed in the doped samples. The temperature dependence of resistivity of the doped crystals show a remarkably different behavior from that of the undoped crystal with the appearance of a minima at lower temperatures, the position of which is fairly constant at different fields. Our data supports the notion that Iridium, which is a bigger atom than rhodium expands the lattice thereby, reduces the electron correlations that existed due to the interaction between closer lying rhodium atoms in the undoped system.     

Effects of electron–electron scattering in wide ballistic microcontacts

We consider effects of electron–electron scattering in wide ballistic microcontacts. Using a semiclassical Boltzmann equation, we obtain a positive correction to the Sharvin conductance that results from electron–electron collisions in the leads. The correction is linearly dependent on temperature at high temperatures T?eV$T?\mathit{eV}$ and proportional to |V|$\left|V\right|$ at high voltages eV?T$\mathit{eV}?T$. Magnetic field leads to strong suppression of this positive correction that results in a positive magnetoresistance in weak fields. As electron–electron scattering affects the conductance, it also influences the noise. At low voltages the noise is defined by the Nyquist relation and at high voltages it is related with the inelastic correction to the current by the Shottky formula δS=2eδI$\delta S=2e\delta I$.     

Quasiparticle lifetime of electron–electron interactions for two-dimensional electron gases with magnetic field

We theoretically study the electron–electron scattering rate τ_ee⁻¹for electrons in a two-dimensional electron gas with a perpendicular magnetic field, within theGWand plasmon-pole approximations, as functions of temperatureT, impurity scattering rate Γ and magnetic fieldB. The τ_ee⁻¹increases with increasingTand increasing Γ, and shows the structure of the Landau levels asBis changed.     

Simulation of electron cyclotron current drive and electron cyclotron resonant heating for the HL-2A tokamak＊

A quasi-linear formalism is developed for relativistic particles. It is self-consistent including spatial diffusion. An attempt is made to simulate the process of electron cyclotron resonant heating （ECRH） and electron cyclotron current drive （ECCD） for the HL-2A tokamak. Temperature oscillating regimes in Tore Supra diagnosed by MHD activity seem to be reproduced in the simulation. The special feature in this paper is to see the resonance in the long time scale for relativistic plasma.     

Monte Carlo particle-based simulations of deep-submicron n-MOSFETs with real-space treatment of electron–electron and electron–impurity interactions

In modern deep-submicron devices, for achieving optimum device performance, the doping densities must be quite high. This necessitates a careful treatment of the short- and long-range electron–electron and electron–impurity interactions. We have shown before that by using a corrected Coulomb force, in conjunction with a proper cutoff range, one can properly account for the short-range portion of the force. Our approach naturally incorporates multi-ion contributions, local distortions in the scattering potential due to the movement of the free charges, and carrier-density fluctuations. The doping dependence of the low-field electron mobility obtained from 3D resistor simulations closely followed the experimental results, thus proving the correctness of our approach. Here, we discuss how discrete impurity effects affect the threshold voltage of ultra-small n-channel MOSFETs with gate lengths ranging from 50 to 100 nm. We find that the fluctuations in the threshold voltage increase with increasing the oxide thickness and substrate doping. The averaging effect over the width of the device leads to significantly smaller fluctuations in the threshold voltage for devices with larger gate width. The observed trends are in agreement with the experimental findings.     

Temperature dependence of the electron effective mass in MnxHg1−xSe

We have investigated the temperature dependence of the electron effective mass in Mn_xHg_1–xSe crystals (0 < x 0.1) in the T=90–300 K temperature range. We have determined that the temperature-dependent changes in the band gap (_g), in the band diagram nonparabolicity, and in the conduction band carrier concentration have a strong effect on the temperature dependence of the carrier effective mass at the Fermi level m ^*=f(T).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 5–9, November, 1987.