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1.
The photon-assisted shot noise through a quantum dot in the Kondo regime is investigated by applying time-dependent canonical transformation and non-crossing approximation technique. A basic formula for the photon-assisted shot noise is obtained. The rich dependence of the shot noise on the external ac field and temperature is displayed. At low temperature and low frequencies, the differential shot noise exhibits staircase behavior. When the temperature increases, the steps are rounded. At elevated frequencies, the photon-assisted tunneling becomes more obvious. We have also found that the Fano factor is enhanced as the ac frequency is enhanced. 相似文献
2.
Photon-assisted shot noise through a quantum dot coupled to Luttinger liquid leads is considered using nonequilibrium-Green-function-method. We find that the effect of ac field on the differential shot noise is different for different intralead electron interaction. The inelastic channels associated with photon-assisted-tunneling can dominate electron transport for some ac parameters. 相似文献
3.
Onac E Balestro F van Beveren LH Hartmann U Nazarov YV Kouwenhoven LP 《Physical review letters》2006,96(17):176601
We present the experimental realization of a quantum dot (QD) operating as a high-frequency noise detector. Current fluctuations produced in a nearby quantum point contact (QPC) ionize the QD and induce transport through excited states. The resulting transient current through the QD represents our detector signal. We investigate its dependence on the QPC transmission and voltage bias. We observe and explain a quantum threshold feature and a saturation in the detector signal. This experimental and theoretical study is relevant in understanding the backaction of a QPC used as a charge detector. 相似文献
4.
We investigate the inelastic transport properties of a quantum dot connected to two leads, based on the combination of a recently developed nonperturbative technique and slave-boson methods involving the approximate mapping of the many-body electron–phonon coupling problem onto a multichannel scattering problem in the Kondo regime. The nonequilibrium Green's function method is adopted in calculations for the inelastic transport processes of electrons in the limit of large Coulomb interaction U→∞ under nonequilibrium conditions. The electron–phonon interactions, which are the main source of the inelasticity, are taken into account. For a single quantum dot, we find that the differential conductance and the shot noise exhibit new structures of peaks and dips which are absent in the case without electron–phonon interactions. 相似文献
5.
Yamauchi Y Sekiguchi K Chida K Arakawa T Nakamura S Kobayashi K Ono T Fujii T Sakano R 《Physical review letters》2011,106(17):176601
We measure the current and shot noise in a quantum dot in the Kondo regime to address the nonequilibrium properties of the Kondo effect. By systematically tuning the temperature and gate voltages to define the level positions in the quantum dot, we observe an enhancement of the shot noise as temperature decreases below the Kondo temperature, which indicates that the two-particle scattering process grows as the Kondo state evolves. Below the Kondo temperature, the Fano factor defined at finite temperature is found to exceed the expected value of unity from the noninteracting model, reaching 1.8±0.2. 相似文献
6.
Q. Chen H. -K. Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):237-248
We have investigated the spectral density of shot noise for an ultra-small quantum dot(QD) system in the Coulomb blockade
regime when irradiated with microwave fields (MWFs) by employing a nonequilibrium Green’s function technique. The shot noise
is sensitive to Coulomb interaction, and the photon-assisted Coulomb blockade behaviour strongly modifies the mesoscopic transport.
We have calculated the first and second derivatives of shot noise in the strong and weak coupling regimes to compare the theoretical
results with existing experimental results. In the strong coupling regime, the first and second derivatives of shot noise
display Fano type peak-valley structures around the charging channel 2E
c
due to Coulomb interaction. When the magnitudes of the MWFs are sufficiently large, the system displays channel blockade
due to photon irradiation. The photon-assisted and Coulomb blockade steps in the noise — as well as the resonant behaviour
in the differential noise — are smeared by increasing temperature. The Coulomb interaction suppresses the shot noise, but
the ac fields can either suppress the shot noise(balanced case) or enhance the shot noise(unbalanced case). The suppression
of shot noise caused by ac fields in the balanced case is greater than that caused by Coulomb interaction in our system. Super-Poissonian
shot noise may be induced due to the compound effects of strong Coulomb interaction and photon absorption-emission processes. 相似文献
7.
The shot noise in the current through a quantum dot is calculated as a function of voltage from the high-voltage Coulomb-blockaded regime to the low-voltage Kondo regime. Using several complementary approaches, it is shown that the zero-frequency shot noise (scaled by the voltage) exhibits a nonmonotonic dependence on voltage, with a peak around the Kondo temperature. Beyond giving a good estimate of the Kondo temperature, it is shown that the shot noise yields additional information on the effects of electronic correlations on the local density of states in the Kondo regime, unaccessible in traditional transport measurements. 相似文献
8.
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. 相似文献
9.
AC field-controlled Andreev tunneling through two serially-coupled quantum dots are investigated theoretically by using the nonequilibrium Green's function method. The photon-assisted Andreev tunneling is studied in detail. It is found that the average current depends distinctly on the interdot coupling. In the weak interdot coupling case, the average current versus the gate voltage exhibit negative peaks on the left-hand side and positive peaks on the right-hand side of the Fermi level. However, in the strong interdot coupling case, the current exhibit both negative and positive peaks on each side of the Fermi level. Furthermore, the system can function as an electron pump capable of transporting electrons through the resonant photon-assisted Andreev tunneling. 相似文献
10.
We study the shot noise of a strongly correlated quantum dot weakly coupled to Luttinger liquid leads in the Kondo regime by means of the extended equation of motion method. A general zero-frequency shot noise formula with good convergence is derived. The shot noise exhibits a non-monotonic dependence on voltage for weak intralead interaction. There is a peak around the Kondo temperature at low voltage when the interaction is very weak, and its height decreases rapidly with the intralead interaction increasing. When the interaction is moderately strong the peak disappears and the shot noise scales as a power law in bias voltage, indicating that the intralead electron interaction suppresses the shot noise. It is possible that the measurements of the shot noise spectrum can extract the information of the intralead interaction. 相似文献
11.
We have investigated the noise properties of the tunneling current through vertically coupled self-assembled InAs quantum dots. We observe super-Poissonian shot noise at low temperatures. For increased temperature this effect is suppressed. The super-Poissonian noise is explained by capacitive coupling between different stacks of quantum dots. 相似文献
12.
Rosa Lpez Ramn Aguado Gloria Platero Carlos Tejedor 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We analyze the conductance (
) of a quantum dot (QD) in an AC potential at finite temperature. The Friedel–Langreth sum rule (FLSR) is generalized to include the effect of an AC potential and finite T. We have solved the Anderson Hamiltonian by means of a self-consistent procedure which fulfills the generalized FLSR. New features are found in the density of states (DOS) and in
when an AC voltage is applied. Our model describes the effect of an AC potential on the transition from Kondo regime to a Coulomb-blockade behaviour as T increases. 相似文献
13.
Here we present a theoretical analysis of the effect of inelastic electron scattering on spin-dependent transport characteristics (conductance, current–voltage dependence, magnetoresistance, shot noise spectrum, Fano factor) for magnetic nanojunction. Such device is composed of molecular quantum dot (with discrete energy levels) connected to ferromagnetic electrodes (treated within the wide-band approximation), where molecular vibrations are modeled as dispersionless phonons. Non-perturbative computational scheme, used in this work, is based on the Green's function theory within the framework of mapping technique (GFT–MT), which transforms the many-body electron–phonon interaction problem into a single-electron multi-channel scattering problem. The consequence of the localized electron–phonon coupling is polaron formation. It is shown that polaron shift and additional peaks in the transmission function completely change the shape of considered transport characteristics. 相似文献
14.
We analyze the frequency-dependent noise of a current through a quantum dot which is coupled to Fermi leads and which is in the Coulomb blockade regime. We show that the asymmetric shot noise, as a function of detection frequency, shows steps and becomes super-Poissonian. This provides experimental access to the quantum fluctuations of the current. We present an exact calculation of the noise for a single dot level and a perturbative evaluation of the noise in Born approximation (sequential tunneling regime but without Markov approximation) for the general case of many levels with charging interaction. 相似文献
15.
Qiao Chen 《Physics letters. A》2008,372(15):2714-2719
We have investigated the spectral density of shot noise of the system with a quantum dot (QD) coupled to two single-wall carbon nanotube terminals, where a rotating magnetic field is applied to the QD. The carbon nanotube (CN) terminals act as quantum wires which open quantum channels for electrons to transport through. The shot noise and differential shot noise exhibit novel behaviors originated from the quantum nature of CNs. The shot noise is sensitively dependent on the rotating magnetic field, and the differential shot noise exhibits asymmetric behavior versus source-drain bias and gate voltage. The Fano factor of the system exhibits the deviation of shot noise from the Schottky formula. The super-Poissonian and sub-Poissonian shot noise can be achieved in different regime of source-drain bias. 相似文献
16.
Hong-Kang Zhao Jian Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):329-342
We have investigated the shot noise affected by the perturbation of
two microwave fields (MWFs) with frequencies ω1 and
ω2, which can be classified as the commensurate and
incommensurate external ac fields. The time-dependent current
correlation function and the spectral density of shot noise have
been obtained. They are very different compared with the
single-field applied system in the nonlinear regime of the ac
potentials. The different photon absorption and emission processes
induce different kinds of noise spectral density. We have performed
the numerical calculations for both commensurate balanced and
unbalanced photon absorptions and emissions. The multi-photon
procedure can be seen clearly from the resonance of shot noise.
Different commensurate number q = ω2/ω1 contributes to
different photon absorption and emission behaviors. It is found that
the asymmetric configuration of shot noise is intimately associated
with the commensurate number q. The differential conductance
appears symmetric and asymmetric behaviors, and the channel blockade
exhibits. The shot noise is large enough to surpass its saturated
value for the unbalanced photon absorption case. The sensitive
behaviors of Fano factor associated with different commensurate
numbers and amplitudes of ac fields signify that the shot noise can
be controlled by external MWFs significantly. 相似文献
17.
H.-K. Zhao L.-L. Zhao J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):441-451
We have investigated the shot noise in the mesoscopic system
composed of a quantum dot (QD) coupled to ferromagnetic terminals
under the perturbation of ac fields. The shot noise has been derived
using the nonequilibrium Green's function (NGF) technique to
describe the spin polarization effect along with photon absorption
and emission processes in the Coulomb blockade regime. We have
examined the influence of spin polarization on the shot noise under
the perturbation of ac fields in the nonadiabatic regime.
The Coulomb blockade effect results
in the modification of shot noise compared with the noninteracting
case. The spin orientation contributes a spin valve effect for
controlling electron tunnelling through this QD, and different
resonant forms appear around the Coulomb blockade channel. The
photon-assisted spin-splitting and spin-polarization effect
contributes a photon-assisted spin valve to adjust the electron
tunnelling current and shot noise. The spin-polarization effect
varies the value of the Fano factor. However, it does not change
the noise type from sub-Poissonian to super-Poissonian. 相似文献
18.
Shot noise of the spin inelastic tunneling through a quantum dot with single molecule-magnet 下载免费PDF全文
We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor in different magnetic fields. It is found that the shot noise and Fano factor exhibit a stepwise behaviour as bias increases in the presence of interaction between the electron and molecule-magnet for a weak magnetic field. As magnetic field becomes strong, a dip is displayed in the shot-noise-bias curve due to the suppression of inelastic shot noise caused by the quantum tunneling of magnetisation. Because of the spontaneous inelastic tunneling at zero bias, a small shot noise occurs, which results in the case of Fano factor F >> 1. Moreover, our results show that the sweeping speed can also influence the shot noise and Fano factor obviously. 相似文献
19.
We study shot noise in tunneling current through a double quantum dot connected to two electric leads.We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics.The approach based on the occupation-state basis,despite being widely used in many previous studies,is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots.In contrast,the calculations using the eigenstate basis are valid for an arbitrary interdot coupling.Using realistic model parameters,we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small.Furthermore,properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment. 相似文献