共查询到20条相似文献,搜索用时 856 毫秒
1.
G. Göppert H. Grabert 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):687-704
We study the linear conductance of single electron devices showing Coulomb blockade phenomena. Our approach is based on a
formally exact path integral representation describing electron tunneling nonperturbatively. The electromagnetic environment
of the device is treated in terms of the Caldeira-Leggett model. We obtain the linear conductance from the Kubo formula leading
to a formally exact expression which is evaluated in the semiclassical limit. Specifically we consider three models. First,
the influence of an electromagnetic environment of arbitrary impedance on a single tunnel junction is studied focusing on
the limits of large tunneling conductance and high to moderately low temperatures. The predictions are compared with recent
experimental data. Second, the conductance of an array of N tunnel junctions is determined in dependence on the length N of the array and the environmental impedance. Finally, we consider a single electron transistor and compare our results for
large tunneling conductance with experimental findings.
Received 2 February 2000 相似文献
2.
T.P. Bigioni L.E. Harrell W.G. Cullen D.K. Guthrie R.L. Whetten P.N. First 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):355-364
Scanning tunneling microscopy (STM) and spectroscopy (STS) have been used to determine the structural and electronic properties
of thiol-passivated 29000 amu gold nanocrystals, both individually and in spontaneously formed quasi-two-dimensional arrays.
Experiments were performed at temperatures of 300 K, 77 K, and 8 K. Even at room temperature, tunneling through these 1.7
nm nanocrystals is shown to give rise to a Coulomb blockade. At cryogenic temperatures, the spectroscopy of the nanocrystals
in arrays and in isolation shows an incremental charging effect (the Coulomb staircase) and evidence is found for quantization
of the electronic states.
Received: 10 September 1998 / Received in final form: 16 February 1999 相似文献
3.
H. Kellay J. Rouch 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):121-129
In this paper we study the influence of the magneto-coupling effect between the longitudinal motion component and the transverse
Landau orbits of an electron on transmission features in single barrier structures. Within the parabolic conduction-band approach,
a modified one-dimensional effective-mass Schr?dinger equation, including the magneto-coupling effect generated from the position-dependent
effective mass of the electron, is strictly derived. Numerical calculations for single barrier structures show that the magneto-coupling
effect brings about a series of the important changes for the transmission probability, the above-barrier quasi-bound states,
and the tunneling time. Through examining the variation of the above-barrier resonant-transmission spectrum with the barrier
width and observing the well-defined Lorentzian line-shape of the above-barrier resonant peaks, we convincingly show that
the above-barrier resonant transmission in single barrier structures is delivered by the above-barrier quasibound states in
the barrier region, just as the below-barrier resonant tunneling in double barrier structures is mediated by the below-barrier
quasi-bound states in the well. Furthermore, we come to the conclusion that the magneto-coupling effect brings about not only
the splitting of the above-barrier quasi-bound levels but also the striking reduction of the level-width of the quasi-bound
states, correspondingly, the substantial increase of the density of the quasi-bound states. We suggest that magneto-coupling
effects may be observed by the measurements of the optical absorption spectrum associated with the above-barrier quasi-bound
states in the single barrier structures.
Received: 26 September 1997 / Revised: 26 November 1997 / Accepted: 15 December 1997 相似文献
4.
We present a generalization of the multiplicative model for velocity increments involving an affine process. The consequences
on the shape of the probability distribution functions for the velocity increments are explored, and shown to be better compatible
with the existence of a scale variation of the skewness.
Received 29 March 1999 and Received in final form 14 September 1999 相似文献
5.
Godfrey Gumbs 《Solid State Communications》2003,128(12):443-448
A model calculation is reported for the tunneling probability of one as well as two interacting electrons from a quantum well within a narrow channel. We discuss the cases when the two electrons are spin polarized or unpolarized by transforming the system to a noninteracting one with the use of quantal density functional theory to obtain an effective single-particle confining potential. A semiclassical approach is used to obtain the tunneling probability from this effective potential. The calculation is motivated by recent measurements of the conductance of an electron gas in a narrow channel but is not meant to explain the anomalous behavior that has been reported since, for example, we deal with a simplified two-level system. Numerical results for the tunneling probability are presented. 相似文献
6.
Rong Lü Hui Hu Jia-Lin Zhu Xiao-Bing Wang Lee Chang Bing-Lin Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):349-361
Resonant quantum tunneling of the Néel vector between nonequivalent magnetic wells is investigated theoretically for a nanometer-scale
single-domain antiferromagnet with biaxial crystal symmetry in the presence of an external magnetic field applied along the
easy anisotropy axis, based on the two-sublattice model. Both the Wentzel-Kramers-Brillouin exponent and the preexponential
factors are evaluated in the instanton contribution to the tunneling rate for finite and zero magnetic fields by applying
the instanton technique in the spin-coherent-state path-integral representation, respectively. The quantum interference or
spin-parity effects induced by the topological phase term in the Euclidean action are discussed in the rate of quantum tunneling
of the Néel vector. In the absence of an external applied magnetic field, the effect of destructive phase interference or
topological quenching on resonant quantum tunneling of the Néel vector is evident for the half-integer excess spin antiferromagnetic
nanoparticle. In the weak field limit, the tunneling rates are found to oscillate with the external applied magnetic field
for both integer and half-integer excess spins. We discuss the experimental condition on the applied magnetic field which
may allow one to observe the topological quenching effect for nanometer-scale single-domain antiferromagnets with half-integer
excess spins. Tunneling behavior in resonant quantum tunneling of the magnetization vector between nonequivalent magnetic
wells is also studied for a nanometer-scale single-domain ferromagnet by applying the similar technique, but in the large
noncompensation limit.
Received 4 June 1999 相似文献
7.
H. Lambaré P. Roche S. Balibar H.J. Maris O.A. Andreeva C. Guthmann K.O. Keshishev E. Rolley 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):381-391
We have studied the nucleation of bubbles in pure superfluid helium-4 at temperatures down to 65 mK. We have found that the
nucleation is a stochastic process, and that at temperatures below 600 mK the nucleation rate is independent of temperature.
These results are consistent with the assumption that the nucleation takes place via quantum tunneling.
Received: 15 November 1997 / Received in final form: 19 December 1997 / Accepted: 22 January 1998 相似文献
8.
Ken-Ichiro Imura 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):155-160
Effects of backward scattering between fractional quantum Hall (FQH) edge modes are studied. Based on the edge-state picture
for hierarchical FQH liquids, we discuss the possibility of the transitions between different plateaux of the tunneling conductance
G. We find a selection rule for the sequence which begins with a conductance (m: integer, p: even integer) in units of e
2/h. The shot-noise spectrum as well as the scaling behavior of the tunneling current is calculated explicitly.
Received 5 October 1999 and Received in final form 19 November 1999 相似文献
9.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
10.
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
11.
J. Favand F. Mila 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):293-299
In order to study the tunneling of electrons through an interacting, 1D, dimerized molecule connected to leads, we consider
the persistent current in a ring embedding this molecule. We find numerically that, for spinless fermions, a molecule with
a gap mostly due to interactions, i.e. a Mott-Hubbard gap, gives rise to a larger persistent current than a molecule with the same gap, but due only to the dimerization.
In both cases, the tunneling current decreases exponentially with the size of the molecule, but more slowly in the interacting
case. Implications for molecular electronic are briefly discussed.
Received: 17 November 1997 / Revised: 16 January 1998 /
Accepted: 16 January 1998 相似文献
12.
T. McAvoy J. Zhang C. Waldfried D.N. McIlroy P.A. Dowben O. Zeybek T. Bertrams S.D. Barrett 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):747-755
The experimental band structure of Mo(112) and the effects by temperature and adsorbate are presented. A surface resonance,
identified as crossing the Fermi level at about 1/3 from to of surface Brillouin zone, was observed to be very sensitive to both contamination and temperature. We find evidence of adsorbate
and temperature induced reconstruction of the Mo(112) surface. Examination of low-energy electron diffraction (LEED) and scanning
tunneling microscopy (STM) data provides evidence for an adsorbate induced reconstruction of the Mo(112) surface with periodicities
consistent with the Fermi level crossing of the surface resonance. The reconstruction is found to occur at coverages as low
as 0.03 Langmuirs of oxygen or carbon. The reconstruction and/or adsorbate affects the density of states and bands near the
Fermi level of a
1 symmetry.
Received 3 March 1999 and Received in final form 1 October 1999 相似文献
13.
Feng Zhai Yong Guo Bing-Lin Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):147-152
We adopt the group velocity approach to the issue of tunneling time in two configurations of magnetic barrier structures,
which are arranged with identical or unidentical building blocks. The effects of an external electric field are also taken
into account. The tunneling time in magnetic barrier structures is found to be strongly dependent on the magnetic configuration,
the applied bias, the incident energy as well as the longitudinal wave vector. The results indicate that for electrons with
equal energy but different incident angles, the tunneling processes are significantly separated in time within the same magnetic
barrier structure. In the configuration arranged with unidentical building blocks, there exists obvious asymmetry of tunneling
time in two opposite tunneling directions. Such a discrepancy of the tunneling time varies distinctly with the longitudinal
wave vector and the applied bias.
Received 4 March 2002 / Received in final form 22 May 2002 Published online 17 September 2002 相似文献
14.
M. Schreier K. Richter G.-L. Ingold R.A. Jalabert 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):387-396
We study the influence of a tunnel barrier on the quantum transport through a circular cavity. Our analysis in terms of classical
trajectories shows that the semiclassical approaches developed for ballistic transport can be adapted to deal with the case
where tunneling is present. Peaks in the Fourier transform of the energy-dependent transmission and reflection spectra exhibit
a nonmonotonic behaviour as a function of the barrier height in the quantum mechanical numerical calculations. Semiclassical
analysis provides a simple qualitative explanation of this behaviour, as well as a quantitative agreement with the exact calculations.
The experimental relevance of the classical trajectories in mesoscopic and microwave systems is discussed.
Received: 23 October 1997 / Received in final form and Accepted: 11 March 1998 相似文献
15.
A. Nittke P. Esquinazi H.-C. Semmelhack A.L. Burin A.Z. Patashinskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):19-30
We have measured the low-temperature (K) specific heat and heat release of small amorphous and crystalline SiO2 particles embedded in Teflon and of Vycor. The temperature and time dependence of these properties have been interpreted
in terms of the tunneling model. We found that the particle size influences the density of states of tunneling systems of
the composite. The smaller the size of the particles the larger is the density of states of tunneling systems P0. Quartz grains with dimensions in the micrometer range show similar glass-like properties as vitreous silica. In comparison
with bulk vitreous silica, Vycor shows a much larger P0 in agreement with the behavior we found for small SiO2 particles. We discuss the implication of our results on the origin of the universal low-temperature properties of glasses.
Received 9 April 1998 相似文献
16.
J. Classen I. Rohr C. Enss S. Hunklinger C. Laermans 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):623-633
Neutron-irradiated quartz is a promising model system to learn more about the low-energy excitations (tunneling states) in
vitreous silica and in similar glasses. We present the first systematic study of the elastic properties of neutron-irradiated
quartz at low frequencies and very low temperatures. Using the vibrating reed technique at frequencies of several kHz we have
measured the sound velocity and internal friction of six quartz crystals irradiated with different neutron doses over a wide
range of temperatures (7 mK-300 K). The results are analyzed using the tunneling model and several extensions of this theory.
Comparisons are made with recent low-frequency measurements on normal and compacted vitreous silica and with ultrasound experiments
on neutron-irradiated quartz.
Received 23 October 1998 相似文献
17.
W. Pfeiffer F. Sattler S. Vogler G. Gerber J.-Y. Grand R. Möller 《Applied physics. B, Lasers and optics》1997,64(2):265-268
Direct illumination of the tunneling gap in an ultrahigh vacuum scanning tunneling microscope with ultrashort pump-probe laser
pulses may offer ultimate spatial and temporal resolution in surface experiments. The electronic bandwidth of the tunneling
gap ( 1 THz) does not limit the time resolution. Our experiments show that multiphoton photoelectron emission from the sample limits
the application of this detection scheme at high laser fluence. However, a substrate specific pump-probe effect in the photoelectron
yield with femtosecond transients is observed on Tantalum and on GaAs(110) surfaces.
Received: 5 November 1996 相似文献
18.
Y. Guo B. Wang B.-L. Gu Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):509-513
We investigate characteristics of spin tunneling time in ZnSe/Ze1-xMnxSe multilayers under the influence of both an electric field and a magnetic field. The results indicate that the tunneling
time shows complicated oscillations and significant spin separation for electrons with different spin orientations traversing
semimagnetic semiconductor heterostructures. It is also shown that the tunneling time exhibits obvious asymmetry in opposite
tunneling directions for electrons tunneling through asymmetric heterostructures, which mainly occurs in resonant regions.
The degree of the asymmetry of the tunneling time is not only spin-polarization dependent but also external-field induced.
Received 10 July 2001 相似文献
19.
A. Rubio S.P. Apell L.C. Venema C. Dekker 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):301-308
We discuss the local cutting of single-walled carbon nanotubes by a voltage pulse to the tip of a scanning tunneling microscope.
The tip voltage ( V) is the key physical quantity in the cutting process. After reviewing several possible physical mechanisms we conclude
that the cutting process relies on the weakening of the carbon-carbon bonds through a combination of localized particle-hole
excitations induced by inelastically tunneling electrons and elastic deformation due to the electric field between tip and
sample. The carbon network releases part of the induced mechanical stress by forming topological defects that act as nucleation
centers for the formation of dislocations that dynamically propagate towards bond-breaking.
Received 6 April 2000 相似文献
20.
J.-L. Zhu R. Lü X.-B. Wang X. Chen L. Chang F.-C. Pu 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):223-231
The tunneling behaviors of the magnetization vector are studied in ferromagnetic systems with trigonal and hexagonal crystal
symmetries, respectively. The Euclidean transition amplitudes between the energetically degenerate easy directions are evaluated
with the help of the dilute instanton-gas approximation. By using the effective Hamiltonian method, the ground-state tunneling
level splittings are clearly shown for each kind of symmetry and are found to depend on the parity of the total spin of the
ferromagnetic particle. The effective Hamiltonian method is demonstrated to be equivalent to the dilute instanton-gas approximation.
Possible relevance to experiments is discussed.
Received: 18 November 1997 / Revised: 18 March 1998 / Accepted: 6 April 1998 相似文献