共查询到20条相似文献,搜索用时 5 毫秒
1.
2.
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. 相似文献
3.
S.-M. Li J. Chen Z.-F. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):157-163
Laser-assisted electron-atomic-hydrogen “elastic" scattering is studied in the first Born approximation. The initial and final
states of projectile electron are described by the Volkov wavefunctions; the dressed state of target described by a time-dependent
perturbative wavefunction in soft photon approximation. The laser modified cross-sections are calculated in two distinct geometries
for laser polarization either parallel or perpendicular to the incident direction of electron. The numerical results shows
that the multiphoton cross-sections oscillate by a few orders over the whole scattering angular region. The results for a
parallel geometry oscillate more frequently in the intermediate angles; while the results for a perpendicular geometry oscillate
more frequently in the forward and backward angles. At large scattering angles, the sum rule of Kroll and Watson is noticeably
violated. The laser modification on summed total cross-section increases with field strength, but decreases with field frequency
and polarization deviation from the incident direction.
Received 18 October 2001 and Received in final form 26 December 2001 相似文献
4.
Electron–acoustic phonon interaction and mobility in stressed rectangular silicon nanowires
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate the effects of pre-stress and surface tension on the electron–acoustic phonon scattering rate and the mobility of rectangular silicon nanowires.With the elastic theory and the interaction Hamiltonian for the deformation potential,which considers both the surface energy and the acoustoelastic effects,the phonon dispersion relation for a stressed nanowire under spatial confinement is derived.The subsequent analysis indicates that both surface tension and pre-stress can dramatically change the electron–acoustic phonon interaction.Under a negative(positive)surface tension and a tensile(compressive)pre-stress,the electron mobility is reduced(enhanced)due to the decrease(increase)of the phonon energy as well as the deformation-potential scattering rate.This study suggests an alternative approach based on the strain engineering to tune the speed and the drive current of low-dimensional electronic devices. 相似文献
5.
The sum-frequency generation (SFG) is theoretically studied in a quantum dot (QD) through the framework of the effective-mass approximation and compact density matrix approach. QD is spherical with the parabolic potential confinement, under applied electric field and in the presence of Rashba spin-orbit interaction (SOI). Using the computed energies and eigenkets, the second-order susceptibility of SFG has been also calculated as a function of radius of QD, spin–orbit interaction strength and the applied electric field. The effects of Rashba SOI strength, radius of QD and the applied electric field on the second-order of susceptibility coefficient are considered. 相似文献
6.
7.
8.
9.
Dragos-Victor Anghel Sergiu Cojocaru 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(12):260
We study the heat power P transferred between electrons and phonons in thin metallic films deposited on free-standing dielectric membranes. The temperature range is typically below 1 K, such that the wavelengths of the excited phonon modes in the system is large enough so that the picture of a quasi-two-dimensional phonon gas is applicable. Moreover, due to the quantization of the components of the electron wavevectors perpendicular to the metal film’s surface, the electrons spectrum forms also quasi two-dimensional sub-bands, as in a quantum well (QW). We describe in detail the contribution to the electron–phonon energy exchange of different electron scattering channels, as well as of different types of phonon modes. We find that heat flux oscillates strongly with thickness of the film d while having a much smoother variation with temperature (T e for the electrons temperature and T ph for the phonons temperature), so that one obtains a ridge-like landscape in the two coordinates, (d, T e ) or (d, T ph ), with crests and valleys aligned roughly parallel to the temperature axis. For the valley regions we find P ∝ T e 3.5 – T ph 3.5 . From valley to crest, P increases by more than one order of magnitude and on the crests P cannot be represented by a simple power law. The strong dependence of P on d is indicative of the formation of the QW state and can be useful in controlling the heat transfer between electrons and crystal lattice in nano-electronic devices. Nevertheless, due to the small value of the Fermi wavelength in metals, the surface imperfections of the metallic films can reduce the magnitude of the oscillations of P vs. d, so this effect might be easier to observe experimentally in doped semiconductors. 相似文献
10.
Non-contact atomic force microscopy (NCAFM) minimizes the physical interaction between the AFM tip and the surface of interest. Several recent studies have reported observation of single atom defects using this technique. The repulsive force is presumably the primary interatomic force (cf. our paper on pseudo-non-contact mode in this issue) responsible for the reported atomic resolution in these studies. The combination of these factors, minimal tip–sample deformation and repulsive force interaction, are responsible for the observation of the single atom defects. In the present study, we show that similar resolution can be achieved utilizing the same two factors but which employs scanning in a surfactant. The method decreases the tip–sample interaction by eliminating the attractive forces between the tip and sample. The surfactant solution induces an electrical double-layer (EDL) on the surface of the tip and sample. This EDL creates additional repulsion that is distributed over a large area, and hence does not contribute noticeably to the image contrast during scanning. However, it does compensate for the high pressures normally experienced by the tip in the absence of surfactant. In addition, the presence of the EDL enhances tip stability during the image scan. This method has been tested on surfaces of such minerals as mica, chlorite, and anhydrite. 相似文献
11.
AbstractThe elastic constants and force constants of an energetic material named as 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) are calculated by first-principles method under the GGA+vdW functional. Based on them, a physical picture to describe the phonon–phonon scattering mechanism is obtained, and a method to evaluate the thermal conductive tensor is developed. The resulting thermal conductivities are in agreement with the available experiments. We find that 20 vibrational modes play important roles in determining the heat exchange process of TATB. The vibrational direction, symmetry, displacement field and the detailed information of the key vibrational modes are obtained. 相似文献
12.
Yu. S. Ponosov A. A. Makhnev S. V. Streltsov V. B. Filippov N. Yu. Shitsevalova 《JETP Letters》2015,102(8):503-507
Electronic Raman scattering in YB6 and in its structural and electronic analog LaB6 has been studied in the temperature range of 10–730 K. The experimental spectra have been compared to those calculated on the basis of ab initio band structures with renormalization owing to the electron–phonon interaction. Good agreement between the calculation and experiment for LaB6 has been obtained throughout the entire temperature range. This allows the determination of the coupling constant λ ep = 0.25. To satisfactorily describe the spectra of electronic light scattering in YB6, it is necessary to introduce an additional electron relaxation channel. In this case, the estimate of the electron–phonon coupling constant λ ep is no more than 0.4; for this reason, a high superconducting transition temperature cannot be explained only by the phonon mechanism. 相似文献
13.
14.
The kinetics of magnetization reversal in bilayer permalloy–niobium microstrips under the effect of both a pulsed magnetic field and an electric current has been experimentally studied. These two cases turn out to be fundamentally different in the types of arising magnetic structures and in the dynamic characteristics of the processes. Such difference is especially striking at low temperatures. An anomalously high rate of the processes under study is observed. According to the suggested qualitative explanation, this effect is due to nonlinear excitations appearing in front of the moving domain wall if the applied electric current lowers the barriers for its motion. For achieving the final conclusions, more accurate quantitative analysis is needed. 相似文献
15.
V. S. Popov V. D. Mur N. B. Narozhnyi S. V. Popruzhenko 《Journal of Experimental and Theoretical Physics》2016,122(3):539-553
The works dealing with the theory of e+e– pair production from vacuum under the action of highintensity laser radiation are reviewed. The following problems are discussed: pair production in a constant electric field E and time-variable homogeneous field E(t); the dependence of the number of produced pairs \({N_{{e^ + }{e^ - }}}\) on the shape of a laser pulse (dynamic Schwinger effect); and a realistic three-dimensional model of a focused laser pulse, which is based on exact solution of Maxwell’s equations and contains parameters such as focal spot radius R, diffraction length L, focusing parameter Δ, pulse duration τ, and pulse shape. This model is used to calculate \({N_{{e^ + }{e^ - }}}\) for both a single laser pulse (n = 1) and several (n ≥ 2) coherent pulses with a fixed total energy that simultaneously “collide” in a laser focus. It is shown that, at n ? 1, the number of pairs increases by several orders of magnitude as compared to the case of a single pulse. The screening of a laser field by the vapors that are generated in vacuum, its “depletion,” and the limiting fields to be achieved in laser experiments are considered. The relation between pair production, the problem of a quantum frequency-variable oscillator, and the theory of groups SU(1, 1) and SU(2) is discussed. The relativistic version of the imaginary time method is used in calculations. In terms of this version, a relativistic theory of tunneling is developed and the Keldysh theory is generalized to the case of ionization of relativistic bound systems, namely, atoms and ions. The ionization rate of a hydrogen-like ion with a charge 1 ≤ Z ≤ 92 is calculated as a function of laser radiation intensity (F and ellipticity ρ. 相似文献
16.
A (2+1)-dimensional electronic system is considered, in which the relation between the Green functions and the conductivity is used. A current–current correlation function, Πμν(B), of the fermion system was obtained in the presence of nonquantized fermion magnetic field B, chemical potential η and gap m. Using this function one can obtain an expression for polarization operator calculated without the magnetic field. The result obtained can be applied for graphene. 相似文献
17.
18.
K. E. Nagaev 《JETP Letters》2017,105(2):137-144
Recent results on the effect of electron–electron collisions on the electric properties of contacts to a twodimensional electron gas with a direct conductivity in the absence of scattering by impurities and boundaries have been reviewed. A correction to the conductance of such contacts owing to the electron–electron scattering can be either positive or negative depending on the contact geometry. The magnitude of this correction strongly depends on the magnetic field. 相似文献
19.
Numerical simulation of the magnetoresistance effect controlled by electric field in p–n junction
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The magnetoresistance effect of a p–n junction under an electric field which is introduced by the gate voltage at room temperature is investigated by simulation. As auxiliary models, the Lombardi CVT model and carrier generationrecombination model are introduced into a drift-diffusion transport model and carrier continuity equations. All the equations are discretized by the finite-difference method and the box integration method and then solved by Newton iteration.Taking advantage of those models and methods, an abrupt junction with uniform doping is studied systematically, and the magnetoresistance as a function of doping concentration, SiO_2 thickness and geometrical size is also investigated. The simulation results show that the magnetoresistance(MR) can be controlled substantially by the gate and is dependent on the polarity of the magnetic field. 相似文献
20.
In this paper, we theoretically study the effect of the in-plane magnetic field on spin polarization in the presence of the Dresselhaus spin–orbit effect. It is shown that the large spin polarization can be achieved in such a nanostructure due to the effects of both the Dresselhaus spin–orbit term and the in-plane magnetic field, but the latter plays a main role in the tunneling process. It is also shown that with the increase of in-plane magnetic field, the degree of spin splitting obviously becomes larger. 相似文献