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1.
P. Schwab R. Raimondi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):5-8
We consider non-equilibrium transport in disordered conductors. We calculate the interaction correction to the current for
a short wire connected to electron reservoirs by resistive interfaces. In the absence of charging effects we find a universal
current-voltage-characteristics. The relevance of our calculation for existing experiments is discussed as well as the connection
with alternative theoretical approaches.
Received 2 September 2002 Published online 29 October 2002 相似文献
2.
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
3.
I.O. Kulik T. Hakioğlu A. Barone 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):219-226
We examine a generic three level mechanism of quantum computation in which all fundamental single and double qubit quantum
logic gates are operating under the effect of adiabatically controllable static (radiation free) bias couplings between the
states. Under the time evolution imposed by these bias couplings the quantum state cycles between the two degenerate levels
in the ground state and the quantum gates are realized by changing Hamiltonian at certain time intervals when the system collapses
to a two state subspace. We propose a physical implementation of the mechanism using Aharonov-Bohm persistent-current loops
in crossed electric and magnetic fields, with the output of the loop read out by using a quantum Hall effect aided mechanism.
Received 26 March 2002 / Received in final form 8 July 2002
Published online 19 November 2002 相似文献
4.
I. Vilfan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):277-284
The properties of
nanowires were investigated with
ab initio calculations based on the density-functional theory.
The molecules build weakly coupled one-dimensional chains, like
and Mo6S9-xIx, and the crystals are
strongly uniaxial in their mechanical and electronic properties.
The calculated moduli of elasticity and resilience along the chain axis are
c11 = 320 GPa and ER = 0.53 GPa, respectively.
The electronic band structure and optical conductivity indicate
that the
crystals are good quasi-one-dimensional conductors.
The frequency-dependent complex dielectric tensor ε, calculated
in the random-phase approximation, shows a strong Drude peak in
ε∥, i.e., for the electric field polarised parallel to
the chain axis, and several peaks related to interband transitions.
The electron energy loss spectrum is weakly anisotropic and has a strong peak
at the plasma frequency ħωp ≈20 eV.
The stability analysis shows that
is metastable against the
formation of the layered
. 相似文献
5.
H.I. Hidmi D.H.E. Gross H.R. Jaqaman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):87-92
The fragmentation of multiply charged atomic sodium clusters of mass 200 is investigated using the Micro-canonical Metropolis
Monte Carlo (MMMC) statistical technique for excitation energies up to 200 eV and for cluster charges up to +9e. In this work we present caloric curves and charged and uncharged fragment mass distributions for clusters with charges 0,
2, and 4. The caloric curves show a dip at the critical point implying a negative specific heat, as expected for finite systems,
while the fragment mass distributions corroborate the picture of a phase transition from one dominant liquid-like cluster
to complete vaporization.
Received 7 November 2001 / Received in final form 4 April 2002 Published online 28 June 2002 相似文献
6.
A. Pundt M. Dornheim M. Guerdane H. Teichler H. Ehrenberg M.T. Reetz N.M. Jisrawi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):333-337
An in situ synchrotron radiation study of quasi-free five nanometer-sized palladium clusters during hydrogen absorption is combined
with molecular dynamics simulations to investigate the structural development. In the diffraction patterns, strong intensity
changes are found that provide evidence for a structural phase transformation that is significantly different from the α--Pd-H bulk phase transition. The structural transition is reversible and driven by the hydrogen concentration. The intensity
changes are consistent with a cubic-to-icosahedral structural phase transition obtained in molecular dynamical simulations
using embedded-atom-method potentials.
Received 15 October 2001 and Received in final form 7 February 2002 相似文献
7.
A. M. Panich A. I. Shames H.-M. Vieth E. Ōsawa M. Takahashi A. Ya. Vul' 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(3):397-402
We report on a nuclear magnetic resonance (NMR) study of
ultrananocrystalline diamond (UNCD) materials produced by detonation
technique. Analysis of the 13C and 1H NMR spectra, spin-spin and
spin-lattice relaxation times in purified UNCD samples is presented. Our
measurements show that UNCD particles consist of a diamond core that is
partially covered by a sp
2-carbon fullerene-like shell. The uncovered
part of outer diamond surface comprises a number of hydrocarbon groups that
saturate the dangling bonds. Our findings are discussed along with recent
calculations of the UNCD structure. Significant increase in the spin-lattice
relaxation rate (in comparison with that of natural diamond), as well as
stretched exponential character of the magnetization recovery, are
attributed to the interaction of nuclear spins with paramagnetic centers
which are likely fabrication-driven dangling bonds with unpaired electrons.
We show that these centers are located mainly at the interface between the
diamond core and shell. 相似文献
8.
B.K. Nikolić V.Z. Cerovski 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):227-238
We report on the comprehensive numerical study of the fluctuation and correlation properties of wave functions in three-dimensional
mesoscopic diffusive conductors. Several large sets of nanoscale samples with finite metallic conductance, modeled by an Anderson
model with different strengths of diagonal box disorder, have been generated in order to investigate both small and large
deviations (as well as the connection between them) of the distribution function of eigenstate amplitudes from the universal
prediction of random matrix theory. We find that small, weak localization-type, deviations contain both diffusive contributions
(determined by the bulk and boundary conditions dependent terms) and ballistic ones which are generated by electron dynamics
below the length scale set by the mean free path ℓ. By relating the extracted parameters of the functional form of nonperturbative
deviations (“far tails”) to the exactly calculated transport properties of mesoscopic conductors, we compare our findings
based on the full solution of the Schr?dinger equation to different approximative analytical treatments. We find that statistics
in the far tail can be explained by the exp-log-cube asymptotics (convincingly refuting the log-normal alternative), but with
parameters whose dependence on ℓ is linear and, therefore, expected to be dominated by ballistic effects. It is demonstrated
that both small deviations and far tails depend explicitly on the sample size--the remaining puzzle then is the evolution
of the far tail parameters with the size of the conductor since short-scale physics is supposedly insensitive to the sample
boundaries.
Received 19 August 2002
Published online 19 November 2002 相似文献
9.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献
10.
E. Cuansing J.-S. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(4):505-513
We study quantum transport in honeycomb lattice ribbons with either
armchair or zigzag edges. The ribbons are coupled to semi-infinite
linear chains serving as the input and output leads and we use a
tight-binding Hamiltonian with nearest-neighbor hops. The input
and output leads are coupled to the ribbons through bar contacts.
In narrow ribbons we find transmission gaps for both types of edges.
The appearance of this gap is due to the enhanced quantum
interference coming from the multiple channels in bar contacts.
The center of the gap is at the middle of the band in ribbons with
armchair edges. This particle-hole symmetry is because bar
contacts do not mix the two sublattices of the underlying bipartite
honeycomb lattice when the ribbon has armchair edges. In
ribbons with zigzag edges the gap center is displaced to the right
of the band center. This breakdown of particle-hole symmetry is
the result of bar contacts now mixing the two sublattices. We also
find transmission oscillations and resonances within the transmitting
region of the band for both types of edges. Extending the length of
a ribbon does not affect the width of the transmission gap, as long
as the ribbon’s length is longer than a critical value when the gap
can form. Increasing the width of the ribbon, however, changes the
width of the gap. In ribbons with zigzag edges the gap width
systematically shrinks as the width of the ribbon is increased. In
ribbons with armchair edges the gap is not well-defined because of
the appearance of transmission resonances. We also find only
evanescent waves within the gap and both evanescent and propagating
waves in the transmitting regions. 相似文献
11.
Y.P. Lee K.W. Kim Y.V. Kudryavtsev V.V. Nemoshkalenko B. Szymański 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):41-50
Comparative study of the solid-state reaction (SSR) in a series of Ti/Ni multilayered films (MLF) with a bilayer period of
0.65-22.2 nm and a constant Ti to Ni sublayer thickness ratio has been performed by using the experimental and computer-simulated
magneto-optical (MO) and optical spectroscopies as well as X-ray diffraction (XRD). It was shown that alloyed-like regions
in an amorphous structure is spontaneously formed near the interfaces between pure elements during the film deposition. The
thickness of this region was estimated as 2-3.8 nm on the basis of the MO and optical studies. The SSR in the Ti/Ni MLF caused
by an annealing at 580 K for 60 min increases the thickness of these interfacial amorphous regions. It was shown that SSR
takes place mainly in the Ti/Ni MLF with relatively “thick” sublayers. The existence of a threshold nominal Ni-sublayer thickness
for observing the equatorial Kerr effect of about 3.0 and 4.5 nm for the as-deposited and annealed Ti/Ni MLF, respectively,
is explained by formation of the nonmagnetic alloyed regions between pure components during the film deposition as a result
of the SSR. For the case of Ti/Ni MLF, the MO and optical approaches turn out to be more sensitive in determining the thickness
of the reacted zone, while XRD is more useful for the structural analysis. It was also shown that the very thin nonreacted
Ni sublayers have different MO properties (and hence electronic structure) from the bulk.
Received 2 May 2001 and Received in final form 21 November 2001 相似文献
12.
P. Galatola G. Coupier M. Saint Jean J.-B. Fournier C. Guthmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(4):549-557
Macroscopic Wigner islands present an interesting
complementary approach to explore the properties of two-dimensional
confined particles systems. In this work, we characterize theoretically
and experimentally the interaction between their basic components, viz.,
conducting spheres lying on the bottom electrode of a plane condenser.
We show that the interaction energy can be approximately described by a
decaying exponential as well as by a modified Bessel function of the
second kind. In particular, this implies that the interactions in this
system, whose characteristics are easily controllable, are the same as
those between vortices in type-II superconductors. 相似文献
13.
G. Michałek B. R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(3):411-419
Conductance and other physical quantities are calculated in double quantum dots (DQD) connected in series in the limit of
coherent tunnelling using a Green's function technique. The inter-dot Coulomb repulsion and the exchange interaction are studied
by means of the Kotliar and Ruckenstein slave-boson mean-field approach. The crossover from the atomic to the molecular limit
is analyzed in order to show how the conductance in the model depends on the competition between the level broadening (dot-lead
coupling) and the dot-dot transmission. The double Kondo effect
was found in the gate voltage characteristics of the conductance in the atomic limit. In the case, when each dot accommodates
one electron, the Kondo resonant states are formed between dots and their adjacent leads and transport is dominated by hopping
between these two resonances. In the molecular limit the conductance vanishes for sufficiently low gate voltages, which means
the Kondo effect disappeared. For small dot-lead coupling the transport characteristics are very sensitive on the influence
of the inter-dot Coulomb repulsion and the position of the local energy level. The
resonance region is widened with increase of the inter-dot Coulomb interactions while the exchange interaction has opposite
influence. 相似文献
14.
L. Simon C. Bena F. Vonau D. Aubel H. Nasrallah M. Habar J. C. Peruchetti 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):351-355
Using scanning tunneling microscopy (STM) and Fourier
Transform STM (FT-STM), we have studied a point defect in
epitaxial graphene grown on silicon carbide substrate. We find a
strong threefold anisotropy in the standing waves generated by the
defect. We discuss possible relations between this anisotropy and
the chirality of the electrons, and how it allows us to identify
the position of the impurity. We extract the quasiparticle energy
dispersion, and give a first experimental proof of the validity of
Fermi liquid theory in graphene for a wide range of energies from
-800 meV to +800 meV. All experimental measurements are
compared and related to theoretical T-matrix calculations. 相似文献
15.
Ben-Yuan Gu Yao Lu Tzong-Jer Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):493-502
We present numerical investigations of the transmission properties of electrons in a normal quantum wire tangentially attached
to a superconductor ring threaded by magnetic flux. A point scatterer with a δ -function potential is placed at node to model
scattering effect. We find that the transmission characteristics of electrons in this structure strongly depend on the normal
or superconducting state of the ring. The transmission probability as a function of the energy of incident electrons, in the
case of a superconductor ring threaded by one quantum magnetic flux, emerges one deep dip, imposed upon the first broad bump
in spectrum. This intrinsic conductance dip originates from the superconductor state of the ring. When increasing the magnetic
flux from one quantum magnetic flux to two, the spectrum shifts toward higher energy region in the whole. This conductance
dip accordingly shifts and appears in the second bump. In the presence of a point-scatterer at the node, the spectrum is substantially
modified. Based on the condition of the formation of the standing wave functions in the ring and the broken of the time-reserve
symmetry of Schr?dinger equation after switching magnetic flux, the characteristics of transmission of electrons in this structure
can be well understood.
Received 6 November 2001 相似文献
16.
Z.Y. Zeng Baowen Li F. Claro 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):401-405
A unified theory for the current through a mesoscopic region of interacting electrons connected to two leads which can be
either ferromagnet or superconductor is presented, yielding Meir-Wingreen-type formulas when applied to specific circumstances.
In such a formulation, the requirement of gauge invariance is satisfied automatically. Moreover, one can judge unambiguously
what quantities can be measured in the transport experiment.
Received 22 August 2002 / Received in final form 14 February 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: phyzengz@nus.edu.sg 相似文献
17.
M. Pudlak R. Pincak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):565-576
The electronic spectra for double-wall zigzag and armchair
nanotubes are found. The influence of nanotube curvatures on the
electronic spectra is also calculated. Our finding that the outer
shell is hole doped by the inner shell is in the difference
between Fermi levels of individual shells which originate from the
different hybridization of π orbital. The shift and rotation
of the inner nanotube with respect to the outer nanotube are
investigated. We found stable semimetal characteristics of the
armchair DWNTs in regard of the shift and rotation of the inner
nanotube. We predict the shift of kF towards the bigger wave
vectors with decreasing of the radius of the armchair nanotube. 相似文献
18.
X. Lü J.H. Chu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):375-378
Thermal conductivity of silicon and porous silicon nanowires based on the equation of phonon radiative transport is theoretically
evaluated. The thermal conductivities of silicon nanowires with square cross-sections are found to match molecular dynamics
simulation results reasonably well. It is shown that the results of meso-porous silicon nanowires are about two orders of
magnitude lower than that of silicon nanowires in a wide range of temperature (50 K-300 K).
Received 24 April 2001 and Received in final form 23 December 2001 相似文献
19.
F. J. Kaiser P. Hänggi S. Kohler 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):201-209
We study numerically the influence of strong Coulomb repulsion on the
current through molecular wires that are driven by external electromagnetic
fields. The molecule is described by a tight-binding model whose first
and last site is coupled to a respective lead. The leads are
eliminated within a perturbation theory yielding a master equation for
the wire. The decomposition into a Floquet basis enables an efficient
treatment of the driving field.
For the electronic excitations in bridged molecular wires, we find that
strong Coulomb repulsion significantly sharpens resonance peaks which broaden again with increasing temperature.
By contrast, it has only a small influence on effects
like non-adiabatic electron pumping and coherent current suppression. 相似文献