134 research outputs found
Electron transport across a quantum wire in the presence of electron leakage to a substrate
We investigate electron transport through a mono-atomic wire which is tunnel
coupled to two electrodes and also to the underlying substrate. The setup is
modeled by a tight-binding Hamiltonian and can be realized with a scanning
tunnel microscope (STM). The transmission of the wire is obtained from the
corresponding Green's function. If the wire is scanned by the contacting STM
tip, the conductance as a function of the tip position exhibits oscillations
which may change significantly upon increasing the number of wire atoms. Our
numerical studies reveal that the conductance depends strongly on whether or
not the substrate electrons are localized. As a further ubiquitous feature, we
observe the formation of charge oscillations.Comment: 7 pages, 7 figure
Formulae for zero-temperature conductance through a region with interaction
The zero-temperature linear response conductance through an interacting
mesoscopic region attached to noninteracting leads is investigated. We present
a set of formulae expressing the conductance in terms of the ground-state
energy or persistent currents in an auxiliary system, namely a ring threaded by
a magnetic flux and containing the correlated electron region. We first derive
the conductance formulae for the noninteracting case and then give arguments
why the formalism is also correct in the interacting case if the ground state
of a system exhibits Fermi liquid properties. We prove that in such systems,
the ground-state energy is a universal function of the magnetic flux, where the
conductance is the only parameter. The method is tested by comparing its
predictions with exact results and results of other methods for problems such
as the transport through single and double quantum dots containing interacting
electrons. The comparisons show an excellent quantitative agreement.Comment: 18 pages, 18 figures; to appear in Phys. Rev.
Abelian-Projected Effective Gauge Theory of QCD with Asymptotic Freedom and Quark Confinement
We give an outline of a recent proof that the low-energy effective gauge
theory exhibiting quark confinement due to magnetic monopole condensation can
be derived from QCD without any specific assumption. We emphasize that the
low-energy effective abelian gauge theories obtained here give the dual
description of the same physics in the low-energy region. They show that the
QCD vacuum is nothing but the dual (type II) superconductor.Comment: 15 pages, Latex, no figures, Talk given at YKIS'97, Non-perturbative
QCD, Kyot
Abelian-Projected Effective Gauge Theory of QCD with Asymptotic Freedom and Quark Confinement
Starting from SU(2) Yang-Mills theory in 3+1 dimensions, we prove that the
abelian-projected effective gauge theories are written in terms of the maximal
abelian gauge field and the dual abelian gauge field interacting with monopole
current. This is performed by integrating out all the remaining non-Abelian
gauge field belonging to SU(2)/U(1). We show that the resulting abelian gauge
theory recovers exactly the same one-loop beta function as the original
Yang-Mills theory. Moreover, the dual abelian gauge field becomes massive if
the monopole condensation occurs. This result supports the dual superconductor
scenario for quark confinement in QCD. We give a criterion of dual
superconductivity and point out that the monopole condensation can be estimated
from the classical instanton configuration. Therefore there can exist the
effective abelian gauge theory which shows both asymptotic freedom and quark
confinement based on the dual Meissner mechanism. Inclusion of arbitrary number
of fermion flavors is straightforward in this approach. Some implications to
lower dimensional case will also be discussed.Comment: 39 pages, Latex, no figures, (2.2, 4.1, 4.3 are modified; 4.4,
Appendices A,B,C and references are added. No change in conclusion
Anomalous Hall effect in Fe/Cu bilayers
The scaling of anomalous Hall resistivity on the longitudinal resistivity has
been intensively studied in the different magnetic systems, including
multilayers and granular films, to examine which mechanism, skew scattering or
side-jump, dominates. The basis of the scaling law is that both the
resistivities are due to the electron scattering at the imperfections in the
materials. By studying of anomalous Hall effect (AHE) in the simple Fe/Cu
bilayers, we demonstrate that the measured anomalous Hall effect should not
follow the scaling laws derived from skew scattering or side-jump mechanism due
to the short-circuit and shunting effects of the non-magnetic layers.Comment: 12 pages, 4 figures;
http://www.springerlink.com/content/1718722u75j24587
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
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