共查询到20条相似文献,搜索用时 15 毫秒
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.
T. S. Li Y. C. Huang S. C. Chang Y. C. Chuang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):73-80
The electronic and thermal properties of AB-stacked bilayer graphene nanoribbons subject to the influences of a transverse
electric field are investigated theoretically, including their transport properties. The dispersion relations are found to
exhibit a rich dependence on the interlayer interactions, the field strength, and the geometry of the layers. The interlayer
coupling will modify the subband curvature, create additional band-edge states, change the subband spacing or energy gap,
and separate the partial flat bands. The bandstructures will be symmetric or asymmetric about the Fermi energy for monolayer
or bilayer nanoribbons, respectively. The inclusion of a transverse electric field will further alter the bandstructures and
lift the degeneracy of the partial flat bands. The chemical-potential-dependent electrical and thermal conductance exhibit
a stepwise increase behavior. Variations in the electronic structures with field strength will be reflected in the electrical
and thermal conductance. Prominent peaks, as well as single-shoulder and multi-shoulder structures in the electrical and thermal
conductance are predicted when varying the electric field strength. The features of the conductance are found to be strongly
dependent on the field strength, the geometry, interlayer interactions and temperature. 相似文献
3.
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
4.
J. Delahaye T. Grenet F. Gay 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):5-19
We perform electrical field effect measurements at 4 K on insulating granular aluminium thin films. When the samples size
is reduced below ≃100 μm, reproducible and stable conductance fluctuations are seen as a function of the gate voltage. Our results suggest that these
fluctuations reflect the incomplete self-averaging of largely distributed microscopic resistances. We also study the anomalous
field effect (conductance dip) already known to exist in large samples and its slow relaxation in the presence of the conductance
fluctuations. Within our measurements accuracy, the two phenomena appear to be independent of each other, like two additive
contributions to the conductance. We discuss the possible physical meaning of this independence and in particular whether
or not this observation is in favor of an electron glass interpretation of slow conductance anomaly relaxations. 相似文献
5.
M. I. Katsnelson 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):151-153
Using the Landauer formula approach, it is proven that
minimal conductivity of order e2/h found experimentally in
bilayer graphene is an intrinsic property. For the case of ideal
crystals, the conductivity turns out to be equal to e2/2h per
valley per spin. A zero-temperature shot noise in bilayer graphene
is considered and the Fano factor is calculated. Its value
1–2/π is close to the value 1/3 found earlier for single-layer
graphene. 相似文献
6.
Yu. O. Klymenko O. Shevtsov 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):383-388
Based on the nearest-neighbor tight-binding approximation, we present exact analytical expressions for transmission coefficients
through piecewise constant step-like and barrier-like electrostatic potentials. In the case of single mode propagation through
semiconducting ribbon families our analytical solutions predict a new kind of resonances. Its features substantially change
the behavior of the transmission coefficients in the range of moderate potentials, which become family-dependent. For semimetal
ribbons our approach predicts no unit propagation. The non-zero backscattering is derived to be proportional as the square
of the potential amplitude applied. 相似文献
7.
Haidong Li 《Physics letters. A》2009,373(5):575-582
The contact conductance between graphene and two quantum wires which serve as the leads to connect graphene and electron reservoirs is theoretically studied. Our investigation indicates that the contact conductance depends sensitively on the graphene-lead coupling configuration. When each quantum wire couples solely to one carbon atom, the contact conductance vanishes at the Dirac point if the two carbon atoms coupling to the two leads belong to the same sublattice of graphene. We find that such a feature arises from the chirality of the Dirac electron in graphene. Such a chirality associated with conductance zero disappears when a quantum wire couples to multiple carbon atoms. The general result irrelevant to the coupling configuration is that the contact conductance decays rapidly with the increase of the distance between the two leads. In addition, in the weak graphene-lead coupling limit, when the distance between the two leads is much larger than the size of the graphene-lead contact areas and the incident electron energy is close to the Dirac point, the contact conductance is proportional to the square of the product of the two graphene-lead contact areas, and inversely proportional to the square of the distance between the two leads. 相似文献
8.
Space-time dispersion of graphene conductivity 总被引:1,自引:0,他引:1
L. A. Falkovsky A. A. Varlamov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):281-284
We present an analytic calculation of the conductivity of pure graphene as a
function of frequency ω, wave-vector k, and temperature for the
range where the energies related to all these parameters are small in
comparison with the band parameter γ≃3 eV, but much larger than
the collision rate τ-1. The simple asymptotic expressions are given
in various limiting cases. For instance, the conductivity for kv0≪
T≪ω is equal to σ(ω,k)=e2/4ħ and independent
of the band structure parameters γ and v0. Our results are also
used to explain the known dependence of the graphite conductivity on
temperature and pressure. 相似文献
9.
Graphene nanodisk is a graphene derivative with a closed edge. The trigonal
zigzag nanodisk with size N has N-fold degenerated zero-energy states.
It can be interpreted as a quantum dot with an internal degree of
freedom. The ground state of nanodisk
is a quasi-ferromagnet, which is a ferromagnetic-like state with a finite but
very long life time. We investigate spin-filter effects in the system
made of nanodisks and leads.
A novel feature of the nanodisk spin filter is that
its spin can be controlled by the spin current.
We propose some applications for spintronics, such as spin memory,
spin amplifier and spin diode.
It is argued that a spin current is reinforced (rectified) by feeding it into a nanodisk spin amplifier (diode).
Graphene nanodisk would be a promising candidate of future electronic and spintronic nanodevices. 相似文献
10.
11.
C. C. Wang S. Jain A. O. Adeyeye 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):305-309
We investigate the magnetoresistance (MR) responses in a ferromagnetic
rectangular ring structure using a four-point probe technique. The measured
MR curves are strongly dependent on the electrical contact geometries used.
The associated MR characteristics are elucidated by a combination of
micromagnetic simulations and resistor-network based model, and the MR
contributions from different portions of the ring were studied
quantitatively. The systematic angular MR measured at the ring corner
further show that the locations of the domain wall nucleation are very
sensitive to the field alignment. 相似文献
12.
T. S. Li S. C. Chang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):497-505
The electronic and transport properties of nanotube-ribbon hybrids
subject to the influences of
a transverse electric field are investigated theoretically.
The energy dispersion relations are found to exhibit rich dependence on the
nanotube-ribbon interactions, the field strength, and the geometry of the hybrids.
The nanotube-ribbon coupling will
modify the subband curvature, create additional band-edge states, and
change the subband spacing or energy gap. The bandstructures are asymmetric and symmetric about the Fermi energy when the
interactions are turned on and off, respectively.
The inclusion of a transverse electric field will further alter
the bandstructures and lift the degeneracy of the partial
flat bands in hybrid (IV). The chemical-potential-dependent
electrical and thermal conductance exhibit a stepwise increase
behavior. Variations in the electronic structures with field
strength will be reflected in the electrical and thermal
conductance. Prominent peaks, as well as single-shoulder and
multi-shoulder structures in the electrical and thermal conductance
are predicted when varying the electric field strength and the
nanotube location. The features of the conductance are found to be
strongly dependent on the field strength, the geometry and the
temperature. 相似文献
13.
S. -H. Ouyang C. -H. Lam J. Q. You 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):67-72
We study electron transport through a quantum dot, connected to non-magnetic leads, in a magnetic field. A super-Poissonian
electron noise due to the effects of both interacting localized states and dynamic channel blockade is found when the Coulomb
blockade is partially lifted. This is sharp contrast to the sub-Poissonian shot noise found in the previous studies for a
large bias voltage, where the Coulomb blockade is completely lifted. Moreover, we show that the super-Poissonian shot noise
can be suppressed by applying an electron spin resonance (ESR) driving field. For a sufficiently strong ESR driving field
strength, the super-Poissonian shot noise will change to be sub-Poissonian. 相似文献
14.
C. -Y. Yang G. -N. Tang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):245-250
We study spin transport in
normal/ferromagnetic/normal/ferromagnetic.../normal
graphene superlattices, which can be realized by putting a series of
magnetic insulator bars on top of a graphene sheet. Owing to
magnetic proximity effect, local exchange splittings will be induced
in the graphene sheet, effectively forming a magnetic graphene
superlattice. The spin polarization of tunneling conductance and the
magneto resistance (MR) exhibit oscillatory behavior with the gate
voltage. The superlattice structure leads to an enhanced spin
polarization and MR ratio, making the magnetic graphene superlattice
become very promising in spintronics applications. 相似文献
15.
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
16.
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
17.
F. Liang Y. H. Yang J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):337-341
We propose an electrical scheme for the generation of a pure spin current without a charge current in a two-terminal device,
which
consists of a scattering region of a two-dimensional electron gas
(2DEG) with Rashba (R) and/or Dresselhaus (S) spin-orbit interaction (SOI)
and two normal leads. The SOI is modulated by a time-dependent gate
voltage to pump a spin current. Based on a tight-binding model and
the Keldysh Green’s function technique, we obtain the analytical
expression of the spin current. It is shown that a pure spin current
can be pumped out, and its magnitude could be modulated by
device parameters such as the oscillating frequency of the SOI, as
well as the SOI strength. Moreover, the spin polarisation direction of
the spin current could also be tuned by the strength ratio between
RSOI and DSOI. Our proposal provides not only a fully electrical means
to generate a pure spin current but also a way to control the spin
polarisation direction of the generated spin current. 相似文献
18.
Multi-band pairing of effectively ultrarelativistic electrons and holes in asymmetrically biased graphene bilayer in strong coupling regime is considered. In this regime, the pairing affects both conduction and valence bands of the both graphene layers, and the order parameter is a matrix, which indices correspond to the bands. For band-diagonal s-wave pairing, we derive the system of multi-band gap equations for the gaps in the valence and conduction bands and solve it in the approximation of constant gaps and in the approximation of separable pairing potential. For a characteristic width of the pairing region of order of magnitude of the chemical potential, the gap values are not much different from single-band BCS estimations. However, if the pairing region is wider, then the gaps can be much larger and depend exponentially on its energy width. We also predict gapped and soliton-like oscillations of a relative phase of the gaps and unpairing of quarter-vortices at Kosterlitz-Thouless transition. 相似文献
19.
A. La Magna I. Deretzis V. Privitera 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):311-316
A method for the study of the electronic transport in strongly coupled electron-phonon systems is formalized and applied to
a model of polyyne chains biased through metallic Au leads. We derive a stationary non equilibrium polaronic theory in the
general framework of a variational
formulation. The numerical procedure we propose can be readily applied if the electron-phonon interaction in the device hamiltonian
can be approximated as an effective single particle electron hamiltonian. Using this approach, we predict that finite polyyne
chains should manifest an
insulator-metal transition driven by the non-equilibrium charging which inhibits the Peierls instability characterizing the
equilibrium state. 相似文献
20.
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