Nonlinear voltage dependence of the shot noise in mesoscopic degenerate conductors with strong electron-electron scattering

It is shown that measurements of zero-frequency shot noise can provide information on electron-electron interaction, because the strong interaction results in the nonlinear voltage dependence of the shot noise in metallic wires. This is due to the fact that the Wiedemann-Franz law is no longer valid in the case of considerable electron-electron interaction. The deviations from this law increase the noise power and make it strongly dependent on the ratio of electron-electron and electron-impurity scattering rates.     

Optical motor: Towards the model of life emerge

We show that strong incoherent broad band light in random media pushes an electron in opposite to an electric force direction. The effective electron-electron interaction becomes attractive in this case, electric current flows in opposite to a voltage drop direction and static polarization is induced in opposition to an applied electric field. The induced effective electron-electron attraction results in the electron coagulation and this light driven self-organization might have been the initial pre-biotic stage in life emerge on Earth.     

Dynamical electron transport through a nanoelectromechanical wire in a magnetic field

We investigate dynamical transport properties of interacting electrons moving in a vibrating nanoelectromechanical wire in a magnetic field. We have built an exactly solvable model in which the electron-electron interaction is considered nonperturbatively and the electric current and mechanical vibration are treated fully quantum mechanically on an equal footing. We demonstrate our theory by calculating the admittance of a finite-size wire, which is influenced by the magnetic field strength, the electron-electron interaction, and the complex interplay between the mechanical and the electrical energy scales. Nontrivial features including sharp resonance peaks appear in the admittance, which may be experimentally observable.     

Theory of interacting donor electrons in the Anderson-localized regime of semiconductors

The current status of investigations for the rival effect of disorder and electron-electron interaction in the intermediate-concentration regime of doped semiconductors is reviewed from the standpoint of transfer-diagonal formulation. In particular, effects of electron-electron interaction on the electronic specific heat and magnetic properties at low temperatures are clarified, and theoretical results are compared with the experimental ones on phosphorusdoped silicon. The formulation to stimulate the Anderson-localized states in the intermediate concentration regime of doped semiconductors by a cluster model is presented, and the results of the computer simulation are discussed in detail.     

Electron-electron interaction in the magnetoresistance of graphene

We investigate the magnetotransport in large area graphene Hall bars epitaxially grown on silicon carbide. In the intermediate field regime between weak localization and Landau quantization, the observed temperature-dependent parabolic magnetoresistivity is a manifestation of the electron-electron interaction. We can consistently describe the data with a model for diffusive (magneto)transport that also includes magnetic-field-dependent effects originating from ballistic time scales. We find an excellent agreement between the experimentally observed temperature dependence of magnetoresistivity and the theory of electron-electron interaction in the diffusive regime. We can further assign a temperature-driven crossover to the reduction of the multiplet modes contributing to electron-electron interaction from 7 to 3 due to intervalley scattering. In addition, we find a temperature-independent ballistic contribution to the magnetoresistivity in classically strong magnetic fields.     

Horizontal rolls in convective flow above a partially heated surface

Considering the nonlinearity arising from the interaction between electrons and lattice vibrations, an effective electronic model with a self-interaction cubic term is employed to study the interplay between electron-electron and electron-phonon interactions. Based on numerical solutions of the time-dependent nonlinear Schroedinger equation for an initially localized two-electron singlet state, we show that the magnitude of the electron-phonon coupling χ necessary to promote the self-trapping of the electronic wave packet decreases as a function of the electron-electron interaction U. We show that such dependence is directly linked to the narrowing of the band of bounded two-electron states as U increases. We obtain the transition line in the χ × U parameter space separating the phases of self-trapped and delocalized electronic wave packets. The present results indicates that nonlinear contributions plays a relevant role in the electronic wave packet dynamics, particularly in the regime of strongly correlated electrons.     

Spin current in an electron waveguide tunnel-coupled to a topological insulator

We show that electron tunneling from edge states in a two-dimensional topological insulator into a parallel electron waveguide leads to the appearance of spin-polarized current in the waveguide. The spin polarization P can be very close to unity and the electron current passing through the tunnel contact splits in the waveguide into two branches flowing from the contact. The polarization essentially depends on the electron scattering by the contact and the electron-electron interaction in the one-dimensional edge states. The electron-electron interaction is treated within the Luttinger liquid model. The main effect of the interaction stems from the renormalization of the electron velocity, due to which the polarization increases with the interaction strength. Electron scattering by the contact leads to a decrease in P. A specific effect occurs when the bottom of the subbands in the waveguide crosses the Dirac point of the spectrum of edge states when changing the voltage or chemical potential. This leads to changing the direction of the spin current.     

The shot noise of the quantum dot weakly coupled to Luttinger liquid

We study the nonequilibrium transport through a single-level quantum dot weakly coupled to Luttinger liquid leads. A general shot noise expression is derived by using nonequilibrium Green function technique. We find that the differential shot noise and differential conductance demonstrate resonant-like behavior as a function of the bias voltage and the quantum dot's energy level for a weak or moderately strong interaction. In the limit of strong electron-electron interaction, the resonant behavior disappears and shows bias-voltage-dependent power law scalings. And the Fano factor also scales as a power law in high bias voltage region. In addition, the Fano factor is enhanced with the electron-electron interaction increased. It implies that the Fano factor can be controlled by tuning the electron-electron interaction in the leads.     

Spontaneous magnetic flux in disordered mesoscopic rings with interacting electrons: Monte Carlo simulations

The nature of a spontaneous magnetic flux in a one-dimensional ring is investigated by the world line Monte Carlo simulations and a mean field treatment of the selfenergy of the circulating current. The effects of disorders, electron-electron interaction and finite temperature are discussed. The results show that both disorder and electron interaction suppress the spontaneous magnetic flux. We are also able to obtain a transition line separating phases with zero and non-zero spontaneous flux in the parameter space.     

Self-trapping of interacting electrons in crystalline nonlinear chains

Considering the nonlinearity arising from the interaction between electrons and latticevibrations, an effective electronic model with a self-interaction cubic term is employedto study the interplay between electron-electron and electron-phonon interactions. Basedon numerical solutions of the time-dependent nonlinear Schroedinger equation for aninitially localized two-electron singlet state, we show that the magnitude of theelectron-phonon coupling χ necessary to promote the self-trapping of theelectronic wave packet decreases as a function of the electron-electron interactionU. We show that such dependence is directly linked to the narrowing ofthe band of bounded two-electron states as U increases. We obtain thetransition line in the χ × U parameter space separatingthe phases of self-trapped and delocalized electronic wave packets. The present resultsindicates that nonlinear contributions plays a relevant role in the electronic wave packetdynamics, particularly in the regime of strongly correlated electrons.     

可控磁性量子点杂质引起的单电子自旋过滤器

本文提出一种基于电子-电子自旋交换相互作用获得自旋极化电流的模型.该方案中,需要两个距离相近的量子点.其中一个是开放系统,另一个是封闭系统.开放系统能完成单电子输运,封闭系统产生比较强的局域磁场,两个系统之间有电子-电子自旋交换相互作用.该相互作用会影响电子输运,从而可以对电子输运产生自旋过滤效应.我们用量子主方程描述开放系统的演化,在有效哈密顿量的基础上,可以得到解析结果.结果显示,在低温条件下,交换相互作用足够强的时候,系统给出的自旋过滤效率接近1.     

The role of electron-electron and electronphonon interactions in the processes of destruction of landau quantization in InAs/AlSb nanostructures

A nonmonotonous temperature dependence of the electron quantum relaxation time is found. The results are interpreted, taking into account the competition between the intrasubband and intersubband electron-electron interaction channels. The experimental nonlinear τ_q (T) and T_D (T) dependences are explained by the appearance of an additional channel of two-dimensional (2D) electron scattering by deformation acoustic phonons under interaction with piezoacoustic phonons.     

Many body theory of photoemission in the quadratic response formalism

Many body Green's function techniques are applied to show that the three current correlation function relating the one photon photoemission current to the applied external field may be expressed by one and two particle correlation properties only for arbitrary many body interactions. An analysis of the double time derivative of the three current correlation function leads to a generalization for arbitrary many body interaction of a formula frequently used for calculations of the photocurrent in the independent electron model. Implications are discussed for the case that only electrostatic electron-electron interactions are present.     

The excitation operator approach to non-Markovian dynamics of quantum impurity models in the Kondo regime

We present the numerical excitation operator method for studying the real time dynamicsof a small interacting quantum system coupled to a non-interacting fermionic reservoir byiteratively solving the Heisenberg equation of motion with the help of excitationoperators. We apply this method to the decoherence dynamics of the single impurityAnderson model in the Kondo regime with a non-Markovian reservoir. We take full account ofthe environmental back-action and the electron-electron interaction, and find that thecoexistence of the strong electron-electron interaction and a non-Markovian reservoirinduces the coherence ringings, which will be suppressed by either driving the system awayfrom the particle-hole symmetric point or changing the reservoir into a Markovian one.     

Electronic polarization reduction of the on site electron-electron repulsion

It is shown that more distant electron interactions strongly affect the self energy of a doubly occupied or vacant site in a half filled band system. This means that the effective electron on site electron-electron interaction as used in the Hubbard Hamiltonian is strongly influenced by electronic polarization effects. We show that these polarization effects are strongly dependent on the state of the system (i.e. semiconducting or metallic) and on the number of “free” carriers. This explains why many materials are metals in spite of a large bare on site electron-electron interaction and provides a means for obtaining a semiconductor to metal transition with increasing temperature.     

Electromagnetically induced transparency in asymmetric double quantum wells

We show how to compute nonlinear optical absorption spectra of an Asymmetric Double Quantum Well (ADQW) in the region of intersubband electronic transitions. The method uses the microscopic calculation of the dephasing due to electron-electron and electron-phonon scattering rates and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities. The polarization dephasing and the corrections to the Rabi frequencies due to the electron-electron interaction are also taken into account. For a proper choice of the QW widths and of the driving fields we obtain electromagnetically induced transparency. This transparency has a very narrow linewidth when a single driving field is applied resonant to the transition between the second and the third subband. In the case of two resonant driving fields or of a driving field resonant between the first and third subband we obtain a large transparency enhancement over the entire absorption spectrum. Results are given for GaAs/GaAlAs QWs and experiments are proposed. Received 21 June 2001 and Received in final form 21 January 2002