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1.
We investigate nonequilibrium noise in a diffusive Andreev interferometer, in which currents emerging from two normal metal/superconductor (N-S) interfaces can interfere. We observe a modulation of the shot noise when the phase difference between the two N-S interfaces is varied by a magnetic flux. This is the signature of phase-sensitive fluctuations in the normal metal. The effective charge inferred from the shot noise measurement is close to q(eff) = 2e but shows phase-dependent deviations from 2e at finite energy, which we interpret as being due to pair correlations. Experimental data are in good agreement with predictions based on an extended Keldysh Green's function approach. 相似文献
2.
We report the first measurement of the dynamical response of shot noise (measured at frequency omega) of a tunnel junction to an ac excitation at frequency omega0. The experiment is performed in the quantum regime, variant Planck's over 2piomega approximately variant Planck's over 2piomega0>kBT at very low temperature T=35 mK and high frequency omega0/2pi=6.2 GHz. We observe that the noise responds in phase with the excitation, but not adiabatically. The results are in very good agreement with a prediction based on a new current-current correlator. 相似文献
3.
K.-H. Yang C.-Z. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(3):409-415
In this paper we investigate the joint effects of the
electron-phonon interaction and an external alternating (ac) gate voltage
on the spectral density of shot noise through a vibrating quantum
dot system, by applying the Lang-Firsov canonical transformation and
the Keldysh nonequilibrium Green's function (NGF) technique. We find
that the effects of the electron-phonon and electron-photon interaction
on the differential shot noise are different. The main resonant peak of
the differential shot noise is decreased only when a time-dependent gate
voltage is imposed on quantum dot. With the ac field amplitude increasing,
the main resonant peak of the differential shot noise decreases. The Fano
factor of the system, which exhibits the deviation of shot noise from the
Schottky formula, is also studied. Super-Poissonian shot noise appears due
to the photon absorption (emission) processes in the low bias voltage region. 相似文献
4.
We show experimentally that even when no bias voltage is applied to a quantum conductor, the electronic quantum partition noise can be investigated with GHz radio frequency excitation. Using a quantum point contact configuration as the ballistic conductor we are able to make an accurate determination of the partition noise Fano factor resulting from the photon-assisted shot noise. Applying both voltage bias and rf irradiation we are able to make a definitive quantitative test of the scattering theory of photon-assisted shot noise. 相似文献
5.
We investigate the effect of electron-phonon inelastic scattering on shot noise in nanoscale junctions in the regime of quasiballistic transport. We predict that when the local thermal energy of the junction is larger than its lowest vibrational mode energy eV(c), the inelastic contribution to shot noise (conductance) increases (decreases) with bias as V (sqrt[V]). The corresponding Fano factor thus increases as sqrt[V]. We also show that the inelastic contribution to the Fano factor saturates with increasing thermal current exchanged between the junction and the bulk electrodes to a value which, for V > V(c), is independent of bias. These predictions can be readily tested experimentally. 相似文献
6.
Pekola JP Nieminen TE Meschke M Kivioja JM Niskanen AO Vartiainen JJ 《Physical review letters》2005,95(19):197004
We have measured the influence of shot noise on hysteretic Josephson junctions initially in the macroscopic quantum tunneling regime. The escape threshold current into the resistive state decreases monotonically with increasing average current through the scattering conductor, which is another tunnel junction. Escape is predominantly determined by excitation due to the wideband shot noise. This process is equivalent to thermal activation (TA) over the barrier at effective temperatures up to about 4 times the critical temperature of the superconductor. The presented TA model is in excellent agreement with the experimental results. 相似文献
7.
Effects of interface bound states on the shot noise in normal metal–low-dimensional Rashba semiconductor tunnel junctions with induced s-wave pairing potential
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《中国物理 B》2019,(5)
We consider the effects of interface bound states on the electrical shot noise in tunnel junctions formed between normal metals and one-dimensional(1 D) or two-dimensional(2 D) Rashba semiconductors with proximity-induced s-wave pairing potential. We investigate how the shot noise properties vary as the interface bound state is evolved from a non-zero energy bound state to a zero-energy bound state. We show that in both 1 D and 2 D tunnel junctions, the ratio of the noise power to the charge current in the vicinity of zero bias voltage may be enhanced significantly due to the induction of the midgap interface bound state. But as the interface bound state evolves from a non-zero energy bound state to a zero-energy bound state, this ratio tends to vanish completely at zero bias voltage in 1 D tunnel junctions, while in 2 D tunnel junctions it decreases smoothly to the usual classical Schottky value for the normal state. Some other important aspects of the shot noise properties in such tunnel junctions are also clarified. 相似文献
8.
We measured shot noise and submillimeter-wave response in a superconducting NbN tunnel junction that had a subharmonic gap structure on the current-voltage (I-V) curve. We found that the observed effective charge, defined from the noise-current ratio, tends to a steplike function of voltage. In the presence of submillimeter-wave radiation of frequency v, novel step structures spaced by hv/2e below and above the half-gap voltage clearly appeared on the I-V curve, overlapping the ordinary photon-assisted tunneling steps spaced by hv/e. Observation of these features provides clear evidence that coherent multiple Andreev reflection processes occur in the NbN tunnel junction with low barrier transparency. 相似文献
9.
G. Bignon F. Pistolesi M. Houzet 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):465-474
We study theoretically the current-noise energy (voltage bias and temperature)
dependence for a N-N'-S structure, where N and S stand for bulk normal metal and
superconductor, respectively, and N' for a short diffusive normal
metal.
Using quasiclassical theory of current fluctuations we determine the
noise for arbitrary distributions of channel transparencies on both
junctions.
The differential Fano factor turns out to depend on both junction
transparencies and the ratio of the two conductances.
We discuss analytically the coherent and incoherent regimes and the
case when one of the two conductances dominates the other one.
Measurement of differential conductance and noise can be used to probe
the channel distribution of the interfaces.
We discuss recent experiments in the light of our results. 相似文献
10.
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
11.
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
12.
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
13.
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
14.
Gomila G Pennetta C Reggiani L Sampietro M Ferrari G Bertuccio G 《Physical review letters》2004,92(22):226601
We report on direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. The present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices. 相似文献
15.
ZHAO Hong-kang 《Frontiers of Physics》2007,2(1):55
Current noise exists in circuits and electronic devices generally, and it exhibits specific features as the system reaches nanometer size. The noise in the nano-system where external ac fields are applied plays an important role, since the properties of the fields and the nano-system together govern the resulting noise. In this paper, we present the derivation of shot noise by employing the non-equilibrium Green s function technique. The more general formulas for the current correlation and noise spectral density are given. The system is composed of a central nano-system coupled to electrodes, and the obtained noise formulas are related to the Green s functions of detailed central regime and the terminals. As an example, we have performed the numerical calculation on a system with a toroidal carbon nanotube coupled to normal metal leads. The noise and Fano factor show intimate relation with the structure of the system and ac fields. The Aharonov-Bohm-like behaviors on the shot noise spectral density and Fano factor are observed to exhibit oscillation structures with period of quantum flux. 相似文献
16.
《中国物理快报》2016,(11)
We consider a superconducting(Josephson) junction driven by the thermal noise with an ac drive current and a dc constant bias current in the overdamped case and in the underdamped case,respectively,and investigate the effect of the constant bias current on the evolution of the net voltage versus the driving frequency.It is shown that,with some suitably selected values of the system's parameters,suitably increasing the absolute value of the constant bias current can lead to the enhancement of resonant activation of the net voltage versus the driving frequency.This result can benefit the investigation for the Josephson junction subjected to the constant bias current(or voltage). 相似文献
17.
Zhao Hong-kang 《Frontiers of Physics in China》2007,2(1):55-62
Current noise exists in circuits and electronic devices generally, and it exhibits specific features as the system reaches
nanometer size. The noise in the nano-system where external ac fields are applied plays an important role, since the properties
of the fields and the nano-system together govern the resulting noise. In this paper, we present the derivation of shot noise
by employing the non-equilibrium Green’s function technique. The more general formulas for the current correlation and noise
spectral density are given. The system is composed of a central nanosystem coupled to electrodes, and the obtained noise formulas
are related to the Green’s functions of detailed central regime and the terminals. As an example, we have performed the numerical
calculation on a system with a toroidal carbon nanotube coupled to normal metal leads. The noise and Fano factor show intimate
relation with the structure of the system and ac fields. The Aharonov-Bohm-like behaviors on the shot noise spectral density
and Fano factor are observed to exhibit oscillation structures with period of quantum flux.
相似文献
18.
H.-K. Zhao Q. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):419-427
We have investigated the spectral density of shot noise for the
system of a quantum dot (QD) coupled to two single-wall carbon
nanotube terminals irradiated with a microwave field on the QD. The
terminal features are involved in the shot noise through modifying
the self-energy of QD. The contributions of carbon nanotube
terminals to the shot noise exhibit obvious behaviors. The novel
side peaks are associated with the photon absorption and emission
procedure accompanying the suppression of shot noise. The shot noise
in balanced absorption belongs to sub-Poissonian, and it is
symmetric with respect to the gate voltage. The differential shot
noise displays intimate relation with the nature of carbon nanotubes
and the applied microwave field. It exhibits asymmetric behavior
for the unbalanced absorption case versus gate voltage. The Fano
factor of the system exhibits the deviation of shot noise from the
Schottky formula, and the structures of terminals obviously
contribute to it. The super-Poissonian and sub-Poissonian shot noise
can be achieved in the unbalanced absorption in different regime of
source-drain bias. 相似文献
19.
H.-K. Zhao L.-L. Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(4):485-494
We have investigated the shot noise spectral density in the parallel
double-quantum-dot (DQD) interferometer threaded with an
Aharonov-Bohm (AB) flux under the perturbation of ac fields. The
derivations are based on the nonequilibrium Green’s function (NGF)
technique in the Coulomb blockade regime. The AB flux and the
perturbation of ac fields together provide a photon-assisted AB
interferometer for controlling the shot noise efficiently. The
signature of the shot noise reflects the intrinsic microstructure of
the DQD system, which plays important roles for the enhancement and
suppression of shot noise. The versatile resonant structures of
shot noise, Fano factor have been revealed to exhibit the
sub-Poissonian and super-Poissonian types of shot noise by
adjusting the gate voltages sequentially. 相似文献
20.
Lindell RK Delahaye J Sillanpää MA Heikkilä TT Sonin EB Hakonen PJ 《Physical review letters》2004,93(19):197002
We have investigated the influence of shot noise on the IV curves of a single mesoscopic Josephson junction. We observe a linear enhancement of zero-bias conductance of the Josephson junction with increasing shot-noise power. Moreover, the IV curves become increasingly asymmetric. Our analysis on the asymmetry shows that the Coulomb blockade of Cooper pairs is strongly influenced by the non-Gaussian character of the shot noise. 相似文献