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1.
T. Prosen D. L. Shepelyansky 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(4):515-518
We establish analogy between a microwave ionization of Rydberg
atoms and a charge transport through a chaotic quantum dot
induced by a monochromatic field in a regime with a potential
barrier between dot contacts.
We show that the quantum coherence leads to dynamical localization
of electron excitation in energy
so that only a finite number of photons is absorbed inside the dot.
The theory developed determines the dependence of localization length
on dot and microwave parameters showing that the microwave power
can switch the dot between metallic and insulating regimes.
ultiphoton ionization and excitation to highly excited states
(e.g., Rydberg states) 相似文献
2.
We have studied the dynamical behaviours of two electrons confined in a double quantum dot driven by rotating magnetic fields in terms of the theory of Lewis-Riesenfeld Hermitian invariants for the explicitly time-dependent Hamiltonian. The coherent spin oscillations in the dot provide a generation source for spin current. Exact solutions obtained allow us to investigate the dynamical properties of the spin localization for various initial localized states. 相似文献
3.
We develop a semiclassical theory for spin-dependent quantum transport to describe weak (anti)localization in quantum dots with spin-orbit coupling. This allows us to distinguish different types of spin relaxation in systems with chaotic, regular, and diffusive orbital classical dynamics. We find, in particular, that for typical Rashba spin-orbit coupling strengths, integrable ballistic systems can exhibit weak localization, while corresponding chaotic systems show weak antilocalization. We further calculate the magnetoconductance and analyze how the weak antilocalization is suppressed with decreasing quantum dot size and increasing additional in-plane magnetic field. 相似文献
4.
Dynamic localization of two electrons in AC-driven triple quantum dots and quantum dot shuttles 下载免费PDF全文
We analyze the dynamic localization of two interacting electrons induced by alternating current electric fields in triple quantum dots and triple quantum dot shuttles. The calculation of the long-time averaged occupation probability shows that both the intra-and inter-dot Coulomb interaction can increase the localization of electrons even when the AC field is not very large. The mechanical oscillation of the quantum dot shuttles may keep the localization of electrons at a high level within a range if its frequency is quite a bit smaller than the AC field. However, the localization may be depressed if the frequency of the mechanical oscillation is the integer times of the frequency of the AC field. We also derive the analytical condition of two-electron localization both for triple quantum dots and quantum dot shuttles within the Floquet formalism. 相似文献
5.
We theoretically analyze electronic spin transport through a triple quantum dot in series, attached to electrical contacts, where the drain contact is coupled to the central dot. We show that current rectification is observed in the device due to current blockade. The current blocking mechanism is originated by a destructive interference of the electronic wavefunction at the drain dot. There, the electrons are coherently trapped in a singlet two-electron dark state, which is a coherent superposition of the electronic wavefunction in the source dot and in the dot isolated from the contacts. Its formation gives rise to zero current and current rectification as the voltage is swept. We analyze this behavior analytically and numerically for both zero and finite magnetic dc fields. On top of that, we include phenomenologically a finite spin relaxation rate and calculate the current numerically. Our results show that triple dots in series can be designed to behave as quantum charge rectifiers. 相似文献
6.
Effect of external noise on the dynamical localization of two coupling electrons in quantum dot array 下载免费PDF全文
The effect of external noise, which is characterized by
an Ornstein--Uhlenbeck process, on the dynamical localization of
two coupling electrons in a quantum dot array under the action of
an ac electric field is studied. A numerical solution of the stochastic
equations is obtained by averaging over stochastic
trajectories. The results show that the external noise may destroy the
dynamical localization, but the anti-noise capacity of the system
is stronger when the two electrons are localized at the ends of
the quantum dot array. 相似文献
7.
Nonequilibrium Green's function is uscd to study spin-polarized electron tunneling through a quantum dot connected to two ferromagnetic electrodes with different orientations via two insulating barriers (FM/I/QD/I/FA.f). Intra-level Coulomb interaction in the dot is considered. General formula of tunneling current which can be used for arbitrary angle between the two electrodes' magnetizations is derived for both the weak and strong intra-dot interactions.We find that the transport current can be divided into two parts: the current with the spin-flip and the current without the spin-flip, which critically depend on the linewidth function near the Fermi level of the ferromagnetic electrodes. If a magnetic field is applied in the quantum dot, different behaviors will be found for weak and strong interactions. 相似文献
8.
We study theoretically the full counting statistics of electron transport through a quantum dot weakly coupled to two ferromagnetic leads, in which an effective nuclear-spin magnetic field originating from the configuration of nuclear spins is considered. We demonstrate that the quantum coherence between the two singly-occupied eigenstates and the spin polarization of two ferromagnetic leads play an important role in the formation of super-Poissonian noise. In particular, the orientation and magnitude of the effective field have a significant influence on the variations of the values of high-order cumulants, and the variations of the skewness and kurtosis values are more sensitive to the orientation and magnitude of the effective field than the shot noise. Thus, the high-order cumulants of transport current can be used to qualitatively extract information on the orientation and magnitude of the effective nuclear-spin magnetic field in a single quantum dot. 相似文献
9.
Linear and nonlinear transport through a quantum dot that is weakly coupled to ideal quantum leads is investigated in the parameter regime where charging and geometrical quantization effects coexist. The exact eigenstates and spins of a finite number of correlated electrons confined within the dot are combined with a rate equation. The current is calculated in the regime of sequential tunneling. The analytic solution for an Anderson impurity is given. The phenomenological charging model is compared with the quantum mechanical model for interacting electrons. The current-voltage characteristics show Coulomb blockade. The excited states lead to additional fine-structure in the current voltage characteristics. Asymmetry in the coupling between the quantum dot and the leads causes asymmetry in the conductance peaks which is reversed with the bias voltage. The spin selection rules can cause a ‘spin blockade’ which decreases the current when certain excited states become involved in the transport. In two-dimensional dots, peaks in the linear conductance can be suppressed at low temperatures, when the total spins of the corresponding ground states differ by more than 1/2. In a magnetic field, an electron number parity effect due to the different spins of the many-electron ground states is predicted in addition to the vanishing of the spin blockade effect. All of the predicted features are consistent with recent experiments. 相似文献
10.
《Physics letters. A》2020,384(24):126607
We study spin-dependent electron transport properties of a thermally driven interacting quantum dot. When an external magnetic field is applied to the quantum dot, the effective transmissions of spin-up and spin-down electrons are separated from each other and have a perfect mirror symmetry with respect to the incident energy at a certain gate voltage. A pure spin current can be induced in the system and modulated by a magnetic field. Under certain magnetic field strengths, a larger pure spin current can be obtained at gate voltages with the values in a range, not just at a specific voltage. These results indicate that the system can be worked as a pure spin current generator. 相似文献
11.
Taking account of the electron--electron (hole) and
electron--hole interactions, the tunneling processes of the main
quantum dot (QD) Coulomb-coupled with a second quantum dot embedded
in n--n junction have been investigated. The eighteen resonance
mechanisms involved in the tunneling processes of the system have
been identified. It is found that the tunneling current depends
sensitively on the electron occupation number in the second quantum
dot. When the electron occupation number in the second dot is tiny,
both the tunneling current peaks and the occupation number plateaus
in the main QD are determined by the intra-resonance mechanism. The
increase of the electron occupation number in the second dot makes
the inter-resonance mechanism participate in the transport processes.
The competition between the inter and intra resonance mechanisms
persists until the electron occupation number in the second dot
reaches around unity, leading to the consequence that the
inter-resonance mechanisms completely dominate the tunneling
processes. 相似文献
12.
D. N. Son N. ArboledaJr W. A. Dino H. Kasai 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):27-35
We consider a two-terminal Aharonov-Bohm (AB) interferometer with a quantum dot inserted in one path of the AB ring.
We investigate the transport properties of this system in and out of the Kondo regime. We utilize perturbation theory to
calculate the electron self-energy of the quantum dot with respect to the intradot Coulomb interaction. We show the expression
of the Kondo temperature as a function of the AB phase together with its dependence on other characteristics such as the
linewidth of the ring and the finite Coulomb interaction and the energy levels of the quantum dot. The current oscillates
periodically as a function
of the AB phase. The amplitude of the current oscillation decreases with increasing Coulomb interaction. For a given temperature,
the electron transport through the AB interferometer
can be selected to be in or out of the Kondo regime by changing the magnetic flux threading perpendicular to the AB ring of
the system. 相似文献
13.
J.M. Villas-Bas Sergio E. Ulloa Alexander O. Govorov 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):333
In this paper we use a density matrix formalism to model the spin photocurrent obtained from a single self-assembled quantum dot photodiode under the influence of an applied strong polarized electromagnetic pulse and a gate voltage. We show that the degree of polarization of the output photocurrent generated by a circularly polarized pulse in a strongly anisotropic quantum dot can be switched as we increase the pulse intensity. A similar effect is observed in a quantum dot with weak anisotropic electron–hole exchange interaction by using an elliptically polarized pulse. In the latter, a shorter pulse is needed, which creates an effective exchange channel through the biexciton. This phenomenon can be used as a dynamical switch to invert the spin-polarization of the extracted current. 相似文献
14.
We study current fluctuations in an interacting three-terminal quantum dot with ferromagnetic leads. For appropriately polarized contacts, the transport through the dot is governed by dynamical spin blockade, i.e., a spin-dependent bunching of tunneling events not present in the paramagnetic case. This leads, for instance, to positive zero-frequency cross correlations of the currents in the output leads even in the absence of spin accumulation on the dot. We include the influence of spin-flip scattering and identify favorable conditions for the experimental observation of this effect with respect to polarization of the contacts and tunneling rates. 相似文献
15.
We develop the general nonequilibrium theory of transport through a quantum dot, including Coulomb blockade effects via a 1/N expansion, where N is the number of scattering channels. At lowest order we recover the Landauer formula for the current plus a self-consistent equation for the dot potential. We obtain the leading corrections and compare with earlier approaches. Finally, we show that to leading and to next leading order in 1/N there is no interaction correction to the weak localization, in contrast to previous theories, but consistent with experiments by Huibers et al. [Phys. Rev. Lett. 81, 1917 (1998)], where N=4. 相似文献
16.
利用非平衡格林函数方法, 理论研究T型双量子点分子Aharonov-Bohm (A-B)干涉仪的电荷及其自旋输运性质. 通过控制T型双量子点分子内量子点间有无耦合, 能够实现在同一电子能级位置处分别出现共振和反共振状态, 根据此性质, 能将体系设计成量子开关器件. 当将两个完全相同的T型双量子点分子分别嵌入A-B干涉仪两臂中时, 磁通取适当数值, 能够出现完全的量子相消干涉. 通过调节量子点能级、左右两电极间的偏压和Rashba自旋轨道相互作用强度, 可对体系自旋流进行调控.
关键词:
非平衡格林函数
T型双量子点分子
Aharonov-Bohm干涉仪
自旋输运 相似文献
17.
W. Zhang J. Gao H.-Z. Guo C.-Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(3):351-356
The electronic structure of dynamic quantum dots formed
by surface acoustic waves potential and the confinement potential
produced by gate voltage has been investigated within the
spin-density-functional theory. We found the addition energy of this
kind quantum dot in general decreases as the electron number
increases, so the basic feature of the quantized acoustoelectric
current with multi-plateaus can be reproduced. The addition energy
needed for a second electron entering into the dynamic quantum dot
is found to be about 2.21 meV, which is in good agreement with
experimental estimations. Moreover, the formation of the Wigner
molecule-like states is observed when the number of electrons in the
dot exceeds three. By the calculated addition energy and the
evolution of the electron density in the presence of a magnetic
field, we also explained the influence of the magnetic field on the
acoustoelectric current appeared in the experiments. 相似文献
18.
X. H. Lu B. H. Teng H. Liu Z. X. Lu Y. H. Rong 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):497-502
The electronic transport in the quantum dot array for an arbitrary number of dots in which the quantum dot A is alternated with the quantum dot B is studied with the exact Green’s function calculation. The algebraic structures of the DC current, the differential conductance, and the density of states for the alternating A/B quantum dot array are obtained analytically. The results show that the two-step-like DC current, the two-main-peak-like differential conductance, and the multi-peak-like density of states will be sensitively modified by the number of dots and the difference for the one-electron level and the resonant width of the quantum dot A with ones of the quantum dot B. 相似文献
19.
A charge-current switch manipulated by the macroscopic quantum coherence of a single-molecule magnet
B. Chang J.-Q. Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(4):515-522
We report a theoretical analysis of electron transport
through a quantum dot with an embedded biaxial single-molecule
magnet, which is coupled to ferromagnetic electrodes of parallel and
antiparallel magnet-configurations. For the antiparallel
configuration of complete polarization it is shown that the
originally prohibited electron transport can be opened up by the
macroscopic quantum coherence of the molecular magnet, which
provides a spin-flipping mechanism. The charge-current and
differential conductance are controllable by variation of the
magnitude and orientation of an external magnetic field, which in
turn manipulates the macroscopic quantum coherence of the molecular
magnet. Moreover, the transport can be switched off at particular
values of the magnetic field, where the tunnel splitting is quenched
by the quantum phase interference of tunnel paths.The transport
current and differential conductance as functions of the
electrode-polarization and magnetic field are extensively studied,
which may be useful in practical applications. A new transport
channel is found in the completely polarized parallel-configuration
induced by the tunnel splitting of molecular magnet and
resonance-peak splits of the conductance are observed in
non-completely polarized configurations. 75.50.Xx Molecular magnets 相似文献
20.
《Physics letters. A》2006,358(1):57-62
We have studied the transport properties of an ac driving double-bridged quantum dot arrays coupled to electronic leads with a uniform magnetic field applied perpendicularly on it using the method based on Floquet approach. The average current as a function of the driving frequency Ω with different parameters of the system can be obtained by numerically solving the corresponding Floquet equation of the system. We have found that the coupling between the two energy levels of the quantum dots on the same bridge site can cause the current peaks degenerate but the magnetic field can eliminate this degeneracy. Thus it is possible for us to manipulate the position and the number of the resonance current peaks in the coupled double-bridged model by varying some of the parameter of the system. 相似文献