Coulomb interaction during coherent transport of electrons in quantum wires

A model is found whereby the Coulomb interaction during electron transport in quantum wires of finite length with current-lead contacts can be taken into account exactly (within the framework of the bosonization method). It is established that the charge density distribution along a wire in the case of the real Coulomb interaction is strongly different from the Luttinger liquid model, where the interaction is assumed to be short-ranged. The charge density near the contacts is found to be much higher than in the model with a short-range interaction, but away from the contacts the two densities are closer to each other. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 184–189 (10 February 1998)     

Coulomb potentials between spherical heavy ions

The Coulomb interaction between spherical nuclei having arbitrary radial nuclear charge distributions is calculated. All these realistic Coulomb potentials are given in terms of analytical expressions and are available for immediate application. So in no case a numerical computation of the Coulomb integral is required. The parameters of the charge distributions are taken from electron scattering analysis. The Coulomb self-energies of the charge distributions used are also calculated analytically in a closed form. For a number of nucleus-nucleus pairs, the Coulomb potentials derived from realistic charge distributions are compared with those normally used in various nucleus-nucleus optical model calculations. In this connection a detailed discussion of the problem how to choose consistently Coulomb parameters for different approximations is given.     

Effects of long range Coulomb interaction on the Peierls instability

The Peierls instability is studied for a one-dimensional tight-binding model of conduction electrons in the half-filled case. The long range Coulomb interaction as well as the electron-phonon coupling are taken into account. It is found that the Peierls distortion is hindered by the long wavelength charge fluctuations due to the Coulomb interaction.     

Study of Coulomb interaction for two diffuse spherical-deformed nuclei

The Coulomb interaction for a spherical—deformed interacting pair is derived assuming realistic nuclear charge distributions. The effect of a finite diffuseness parameter is described either by the folding product of spherical or deformed sharp-surface distribution and a spherical short-range function or by using a Fermi two-parameter distribution function. The approximate solutions obtained using these categories of charge distributions are then compared to the numerical solution obtained within the framework of the double-folding model. We found that the finite surface diffuseness parameter affects slightly the inner region of the total Coulomb potential, while it produces large errors in calculating the Coulomb form factors used frequently in nuclear reactions and fusion numerical codes. The text was submitted by the authors in English     

Impurity scattering,Friedel oscillations and RKKY interaction in graphene

We investigate Friedel Oscillations (FO) surrounding a point scatterer in graphene. We find that the long-distance decay of FO depends on the symmetry of the scatterer. In particular, the FO of the charge density around a Coulomb impurity show a faster, δρ∼1/ r³, decay than in conventional 2D electron systems. In contrast, the FO of the exchange field which surrounds atomically sharp defects breaking the hexagonal symmetry of the honeycomb lattice decay according to the 1/r² law. We discuss the consequences of these findings for the temperature dependence of the resistivity of the material and the RKKY interaction between magnetic impurities.     

Cavity‐photon contribution to the effective interaction of electrons in parallel quantum dots

A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron‐electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field.     

Coulomb interaction between conduction electrons andf-electrons in the Anderson impurity model

The influence of the Coulomb interaction between localf-electrons and conduction electrons on the dynamical properties off-electrons is investigated for the Anderson impurity model. An equation-of-motion technique is used to treat simultaneously the Coulomb interaction and the hybridization. We find that the Abricosov-Suhl resonance remains sharp but is reduced in size while the charge excitation peak of thef-electrons is broadened.     

On the Coulomb interaction in granular systems

The previous theories on the behaviour of the conductivity of high-resistivity granular metals are analysed in terms of the Coulomb interaction between the charge carriers. In these theories a non-interacting system of carriers is considered, but it turns out that the Coulomb interaction is involved elsewhere in the calculations. Leaving out this interaction is shown to be a rather wrong assumption. The application of the Efros-Shklovskii theory leads to a real Coulomb gap. A second method is used to confirm the existence of this gap, which width is determined. The results we obtain seem to be consistent with those obtained on the systems with impurities.     

Effects of positron phonon interaction in metals

We investigate the importance of positron phonon interaction for the many body effects observed in positron annihilation in metals. The interaction is formulated as the screened Coulomb interaction of the positron with the polarization charge of the metal produced by lattice vibrations. The phonon contribution to the effective mass is found negligibly small. Due to the interaction with phonons the equilibrium positron momentum distribution deviates from a Boltzmann distribution leading to a larger thermal smearing of the annihilation curves than expected from the rather small effective mass. The positron energy loss in the thermalization process due to phonon excitation is discussed and found comparable to the energy loss due to the excitation of electron hole pairs in the experimentally interesting temperature range.     

Physical Features of Binary Coulomb Crystals: Madelung Energy,Collective Modes and Phonon Heat Capacity

Electrostatic energy, collective modes, and thermodynamic functions of a Coulomb crystal with equal number of ions of two different types and uniform charge‐compensating electron background are studied using harmonic lattice model. Simple cubic and hexagonal lattices with two different ions in the elementary cell (we denote these lattices sc2 and h2, respectively) are considered. The static sc2 lattice is more tightly bound than the h2 one at any charge ratio of the constituent ions. The phonon spectra depend on the ion charge and mass ratio. An analysis shows that these binary Coulomb crystals are stable, if the charge ratio is not too different from 1 (about 3.6 for sc2 and 1.3 for h2 lattices) regardless of the mass ratio. Heat capacity of the sc2 lattice is obtained by numerical integration over the first Brillouin zone as a function of temperature and charge and mass ratios. Well known classic and quantum asymptotes of the heat capacity are reproduced, and the dependence of the coefficient in the Debye T³ law on charge and mass ratios is presented (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurement of the interaction potential of microspheres in the sheath of a rf discharge

The interaction potential of two microspheres that are levitated in the sheath region of a radio frequency (rf) argon discharge is studied experimentally by analyzing their trajectories during head-on collisions. It is shown that the interaction parallel to the sheath boundary can be described by a screened Coulomb potential. Thus, values for an effective charge and a screening length can be obtained. The horizontal part of the interaction potential has been determined for several plasma conditions. There is no evidence for an attractive part in the potential within the accuracy of the present measurements and the given plasma conditions.     

Mechanical model of the Lorentz force and Coulomb interaction

The centripetal and Coriolis accelerations experienced by a cart traveling over a rotating turntable are usually calculated proceeding from the known kinematics of the problem. Respective forces can be regarded as due to the entrainment of the cart in the moving solid environs. We extend the approach to the general case of a particle entrained in the flow of the surrounding medium. The expression for the driving force on the particle obtained from the kinematics of the entrainment prescribed appears to be isomorphic to the Lorentz and Coulomb force on a positive electric charge. The inverse direction of the electromagnetic force on a negative charge implies that a growing applied flow induces the upstream motion of the particle. A possible microscopic mechanism for it may be the Magnus force dynamics of a kink in a vortex tangle. The loop on a straight vortex filament can be taken as a model of the electron, the loop with a cavitation models the positron. The Lorentz force is concerned with the Coriolis acceleration. The Coulomb interaction is due to the centripetal or centrifugal force that arises in the turbophoresis of the kink in the perturbation field generated in the medium by the center of pressure.      

Rate of intersubband transitions of charge carriers in semiconductor quantum wells as a result of their Coulomb interaction

The intersubband scattering of charge carriers in semiconductor quantum wells as a result of their Coulomb interaction has been theoretically investigated. Analytical expressions for the rate of intersubband transitions in the process of electron—electron and electron—hole collisions have been derived in the Born approximation. The theoretical and experimental data on the photoluminescence decay time, obtained for the case of a nondegenerate distribution of charge carriers, were in qualitative agreement. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 782–787, November–December, 2005.     

Time-dependent transport through a quantum dot: influence of the Coulomb interaction on the quantum dot charge states

We consider the electron transport through one-level quantum dot, out of the Kondo regime, under the influence of the external microwave fields. The influence of the intra-dot Coulomb electron-electron interaction is studied using the equation of motion method for appropriate correlation functions. The formula for the current and the closed set of the integro-differential equations for the expectation values of the quantum dot charge states are given. The most characteristic feature of these time-averaged expectation values is an appearance of the additional structure (sidebands) on the curves of the derivatives of the expectation values with respect to the gate voltage. The sidebands structure formed on both sides of the ‘ionization’ and ‘affinity’ quantum dot levels are also found on the current and differential conductance curves.     

The influence of the s-d(f) coulomb interaction on the transition element compound superconductive critical temperature

The influence of s-d Coulomb interaction on the superconductive critical temperature T_c of transition element compounds and their dilute alloys was investigated in the frame of Anderson model. Coulomb interaction of electrons with opposite spins on the same atom was considered in a ladder approximation valid when hybridization is sufficiently small while s-d Coulomb interaction has led to the “parquet” summation. It is shown that s-d Coulomb interaction results in the decrease of T_c and hence the electron mechanism of superconductivity seems to be noneffective in systems under consideration.     

Localized charge inhomogeneities and phase separation near a second-order phase transition

Localized charge inhomogeneities and phase separation are described in the framework of the phenomenological theory of phase transitions. It is shown that Coulomb interaction determines the charge distribution and the characteristic size of the emerging inhomogeneities. Phase separation associated with charge segregation becomes possible because of a high dielectric constant and a low excess charge density in the localization region. The phase diagram of the system is calculated, and estimates are obtained for the gain in energy associated with the emerging state. The role of Coulomb interaction is exposed, and corresponding estimates are given.     

Spin-polarized current through a lateral double quantum dot with spin–orbit interaction

We study the spin-polarized current through a vertical double quantum dot scheme. Both the Rashba spin–orbit (RSO) interaction inside one of the quantum dots and the strong intradot Coulomb interactions on the two dots are taken into account by using the second-quantized form of the Hamiltonian. Due to the existence of the RSO interaction, spin-up and spin-down electrons couple to the external leads with different strengths, and then a spin polarized current can be driven out of the middle lead by controlling a set of structure parameters and the external bias voltage. Moreover, by properly adjusting the dot levels and the external bias voltages, a pure spin current with no accompanying charge current can be generated in the weak coupling regime. We show that the difference between the intradot Coulomb interactions strongly influences the spin-polarized currents flowing through the middle lead and is undesirable in the generation of the net spin current. Based on the RSO interaction, the structure we propose can efficiently polarize the electron spin without the usage of any magnetic field or ferromagnetic material. This device can be used as a spin-battery and is realizable using the present available technologies.     

Electron-phonon interaction and antiferromagnetic correlations

We study effects of the Coulomb repulsion on the electron-phonon interaction (EPI) in the Holstein-Hubbard model, using the antiferromagnetic (AF) dynamical mean-field approximation. AF correlations strongly enhance EPI effects on the electron Green's function with respect to the paramagnetic correlated system, but the net effect of the Coulomb interaction is a moderate suppression of the EPI. Doping leads to additional suppression. In contrast, the Coulomb interaction strongly suppresses EPI effects on phonons, but the suppression weakens with doping.     

Collisional Lifetimes of Elementary Excitations in Two-Dimensional Systems in the Field of a Strong Electromagnetic Wave

A two-dimensional system with two nonequivalent valleys in the field of a strong circularly polarized electromagnetic wave is considered. It is assumed that the optical selection rules for a given polarization of light allow band-to-band transitions only in valleys of one, optically active, type (two-dimensional layer based on transition metal dichalcogenides, gapped graphene, etc.). This leads to the formation of photon-coupled electron–hole pairs, or an “optical insulator” state. It is assumed that the valleys of the second type (optically inactive) are populated with an equilibrium electron gas. The relaxation of elementary excitations in this hybrid system consisting of an electron gas and a gas of electron–hole pairs caused by the Coulomb interaction between the particles is investigated.