共查询到20条相似文献,搜索用时 15 毫秒
1.
A. H. Phillips N. A. I. Aly K. Kirah H. E. El-Sayes 《中国物理快报》2008,25(1):250-253
The transport property of a quantum dot under the influence of external time-dependent field is investigated. The mesoscopic device is modelled as semiconductor quantum dot coupled weakly to superconducting leads via asymmetric double tunnel barriers of different heights. An expression for the current is deduced by using the Landauer-Buttiker formula, taking into consideration of both the Coulomb blockade effect and the magnetic field. It is found that the periodic oscillation of the current with the magnetic field is controlled by the ratio of the frequency of the applied ac-field to the electron cyclotron frequency. Our results show that the present device operates as a radio-frequency single electron transistor. 相似文献
2.
A. B. Pashkovskii 《JETP Letters》2011,93(10):559-563
The dependence of the width and shape of the resonance levels of asymmetric double-barrier resonance-tunneling structures
with high narrow barriers on the amplitude of the resonance microwave field and specific features of the electron transport
in the case of ballistic passage of electrons near the resonance levels has been investigated. It has been found that a resonance
level can be first broadened significantly and be further split into two absolutely transparent levels with an increase in
the microwave field amplitude. The conditions have been formulated under which nonresonance scattering channels near the resonance
levels also become absolutely transparent. 相似文献
3.
A. D. Chepelianskii D. L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):261-270
On a basis of extensive analytical and numerical
studies we show that a linear-polarized microwave field
creates a stationary magnetization in mesoscopic ballistic quantum
dots with two-dimensional electron gas being at a thermal equilibrium.
The magnetization is proportional to a number of electrons
in a dot and to a microwave power.
Microwave fields of moderate strength create
in a one dot of few micron size a magnetization
which is by few orders of magnitude larger than
a magnetization produced by persistent currents.
The effect is weakly dependent on temperature and
can be observed with existing experimental techniques.
The parallels between this effect and ratchets
in asymmetric nanostructures are also discussed. 相似文献
4.
We theoretically study the electron transport properties for two coupled single-walled caxbon nanotube quantum dots connected to metallic electrodes under the irradiation of an external electromagnetic field at low tempera- tures. Using the standaxd nonequilibrium Green's function techniques, we examine the time-averaged transmission coefficient and linear conductance. It is shown that by some numerical examples, the photon-assisted inter-dot coupling causes Fano resonance and the conductance of the system is sensitive to the external field parameters. The transport dependence on the external field parameters may be used to detect the high-frequency microwave irradiation. 相似文献
5.
L. Ermann D. L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(3):357-362
Using extensive Monte Carlo simulations we study numerically and analytically a
photogalvanic effect, or ratchet, of directed electron transport induced by a microwave radiation
on a semidisk Galton board of antidots in graphene. A comparison between usual two-dimensional
electron gas (2DEG) and electrons in graphene shows that ratchet currents are comparable at very low
temperatures. However, a large mean free path in graphene should allow to have a strong ratchet
transport at room temperatures. Also in graphene the ratchet transport emerges even for unpolarized
radiation. These properties open promising possibilities for room temperature graphene based sensitive
photogalvanic detectors of microwave and terahertz radiation. 相似文献
6.
研究高功率微波作用下等离子体中的雪崩效应,对于研究等离子体防护技术具有重要意义.通过采用等离子体流体近似方法,建立等离子体中的波动方程、电子漂移-扩散方程和重物质传递方程,表征电磁波在等离子体中的传播以及等离子体内部带电粒子的变化情况,分析研究了高功率微波作用下雪崩效应的产生过程和变化规律.研究表明,入射电磁波功率决定了雪崩效应的产生;初始电子密度能够影响雪崩效应产生的时间;入射电磁波的激励作用初始表现为集聚效应,当激励能量积累到一定阈值时,雪崩效应才会产生;在雪崩效应产生过程中,等离子体内部电子密度的变化非常迅速并且比较复杂.雪崩效应产生后,等离子体内截止频率会远超过入射波频率,电磁波不能在等离子体中传播,从而起到防护高功率微波的效果. 相似文献
7.
A. Fraenkel E. Finkman G. Bahir A. Brandel G. Livescu M.T. Asom 《Superlattices and Microstructures》1992,12(4)
The transport of hot electrons in the AlxGa1−xAs barriers above the wells in a multiple quantum well (MQW) structure is investigated. The structures that are studied are asymmetric quantum well infrared detectors. The transport of the hot electrons normal to the layers is strongly dependent on both voltage and well shape. It is suggested that the key parameter which affects the transport properties is the dwell time of the electrons in the continuum, above the well region. This is most readily seen in asymmetric MQW structures, in which the dwell time under an applied bias depends very strongly on bias polarity. Calculations of electron transmission coefficient and dwell time show that the electron mean free path in asymmetric wells is much larger in positive bias than in a negative one. Employing this model, we achieve a very good fit to experimental data. 相似文献
8.
The plasmon microwave response of symmetric and asymmetric stripes of two-dimensional electrons with different boundary conditions
has been studied. The symmetric case corresponds to stripes either without ohmic contacts or with ohmic contacts on both sides,
while the contact in asymmetric stripes is present only on one side. It has been shown that there is a frequency shift of
the observed plasma modes in asymmetric stripes. The lowest-frequency mode becomes a previously unobserved mode for which
the quarter wavelength of the plasmon coincides with the length of the stripe. The behavior of the lowest mode and its multiple
frequencies in asymmetric stripes has been studied under variation of the magnetic field, electron density, and temperature
and size of the stripes. The results indicate that all plasma modes in symmetric and asymmetric stripes have the same physical
nature. 相似文献
9.
Electron ratchet effect in semiconductor devices and artificial materials with broken centrosymmetry
A.M. Song 《Applied Physics A: Materials Science & Processing》2002,75(2):229-235
Studies on nonlinear electron transport in nanometer-sized semiconductor devices with broken centrosymmetry are reviewed.
In these devices, an applied alternating (rocking) electric field induces a net flow of electrons in the direction perpendicular
to that of the applied field. Such an electron ratchet effect has been observed in a number of differently designed devices,
fabricated from two types of semiconductor material systems. The functionality is interpreted with an extended Büttiker–Landauer
formula. We show that the devices operate at both cryogenic and room temperatures and at frequencies up to at least 50 GHz.
Based on a similar microscopic mechanism, we have also constructed, to the best of our knowledge, the first artificial electronic
nanomaterial that operates at room temperature. The promising possibilities for practical applications, such as rectification,
microwave detection, second-harmonic generation, etc., are also discussed.
Received: 16 January 2002 / Accepted: 11 February 2002 / Published online: 22 April 2002 相似文献
10.
Rectification of microwave radiation by asymmetric ballistic dot is studied at different frequencies (1-40 GHz), temperatures, and magnetic fields. Dramatic reduction of the rectification is found in magnetic fields at which the cyclotron radius of electron orbits at the Fermi level is less than the size of the dot. With respect to the magnetic field, both symmetric and antisymmetric contributions to the rectification are presented. The symmetric part changes significantly with microwave frequency omega at omegatau_{f}>/=1, where tau_{f} is the time of the ballistic electron flight across the dot. The results lead consistently towards the ballistic origin of the effect, and can be explained by strongly nonlocal electron response to the microwave electric field, which affects both speed and direction of the electron motion inside the dot. 相似文献
11.
Photoconductivity of a two-dimensional electron system with spin-orbit coupling in AC magnetic field
The response of an electron system to a dc probe field is analyzed in the case when an initial deviation of conduction-electron spin degrees of freedom from equilibrium in a microwave magnetic field induces combined resonance transitions in the electron system. It is shown that a perturbation of spin degrees of freedom is converted into kinetic energy and modifies transport coefficients, leading to oscillations of diagonal components of the conductivity tensor. 相似文献
12.
免掺杂、非对称异质接触的新型太阳电池由于近几年的飞速发展,理论转化效率已达到28%,具有较大的发展空间,引起了人们的重视.由于传统晶硅太阳电池产业存在生产设备成本高、原材料易燃易爆等诸多限制,市场对太阳电池产业低成本、绿色无污染的期待越来越高,极大地增加了免掺杂、非对称异质接触的新型太阳电池研究和开发的必要性.为了进一步加快免掺杂、非对称异质接触晶体硅太阳电池的研究进度,本文对其发展现状进行了综述,着重讨论了过渡金属氧化物(TMO)载流子选择性运输的基本原理、制备技术以及空穴传输层、电子传输层和钝化层对基于TMO构建的免掺杂、非对称异质接触(DASH)太阳电池性能的影响,以期对电池的工作机理、材料选择有更深刻的认识,为新型高效的DASH太阳电池制备提供指导. 相似文献
13.
《Physics letters. A》1998,244(5):432-436
In low-dimensional electron systems with an asymmetric quantizing potential in a magnetic field, the electromotive force appears in the presence of a standing acoustic wave [O.V. Kibis, Phys. Lett. A 237 (1998) 292]. The consequence of this quantum macroscopic effect is that homogeneous heating of the electron system leads to the emergence of a phonon drag of electrons, which leads to a new class of electron transport phenomena. 相似文献
14.
A hysteretic cyclotron resonance (CR) is discovered in a laterally confined high mobility two-dimensional electron gas (2DEG) in GaAs/AlGaAs heterostructures. The hysteresis and switching phenomena are observed in microwave radiation (36 GHz) transmission at temperature 1.8–25 K. It is found that the hysteresis is accompanied by long-lived, microwave-induced changes of the 2DEG density. These density changes is attributed to a modification of electron vertical transport processes in heterostructures under the microwave heating of the 2DEG. A phenomenological model based on the 2DEG density-dependent CR, describes reasonably the main experimental findings. 相似文献
15.
W. Zhang H.Z. Guo H. Yuan C.Y. Zhang C. Lu J. Gao 《Solid State Communications》2009,149(47-48):2228-2231
We report the transport properties of a surface acoustic wave based single electron transport device, which contains an unintentional quantum dot induced by background impurity potential fluctuations. It is found that the presence of the impurity potential can cause a deviation of the acoustoelectric current from its quantized value. Through the charging effect of the quantum dot induced by the impurity, we get an approximate relationship between the applied gate voltage and its corresponding electrostatic potential barrier height, together with the Coulomb charging energy needed to add a second electron into the dynamic quantum dot. Moreover, the amplitude of the surface acoustic wave is also estimated within a simple model. 相似文献
16.
The synchronization (CS) and anti-synchronization (AS) of two non-identical inertial ratchets moving in different asymmetric potentials and transporting particles chaotically is demonstrated based on a technique derived from nonlinear control theory. It is shown that in the CS state, particle current is enhanced; while in the AS state, the particles transport current in different directions, suggesting that AS phenomenon could be exploited as a mechanism for particle separation. 相似文献
17.
18.
We investigate the degree of coherence of electronic transport through a quantum dot (QD) in the presence of an intradot electron-electron interaction. By using an open multiterminal Aharonov-Bohm (AB) setup, we find that the intradot interaction does not induce any dephasing effect and the electron transport through the QD is fully coherent. We also observe that the asymmetric amplitude of the AB oscillation in the conductance through the two-terminal AB setup originates from the interplay between the confined structure and the electron-electron interaction. Thus, one cannot associate a dephasing process with this asymmetric amplitude, as has been done in previous studies. 相似文献
19.
H.-K. Zhao J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):513-524
The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum
dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation
values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium
Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The
time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current
and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar
properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum
SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single
CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely.
Received 28 May 1998 相似文献
20.
We predict the possibility to generate a finite stationary spin current by applying an unbiased ac driving to a quasi-one-dimensional asymmetric periodic structure with Rashba spin-orbit interaction and strong dissipation. We show that under a finite coupling strength between the orbital degrees of freedom the electron dynamics at low temperatures exhibits a pure spin ratchet behavior, i.e., a finite spin current and the absence of charge transport in spatially asymmetric structures. It is also found that the equilibrium spin currents are not destroyed by the presence of strong dissipation. 相似文献