10,726 research outputs found
Weak localization in a system with a barrier: Dephasing and weak Coulomb blockade
We non-perturbatively analyze the effect of electron-electron interactions on
weak localization (WL) in relatively short metallic conductors with a tunnel
barrier. We demonstrate that the main effect of interactions is electron
dephasing which persists down to T=0 and yields suppression of WL correction to
conductance below its non-interacting value. Our results may account for recent
observations of low temperature saturation of the electron decoherence time in
quantum dots.Comment: published version, 10 page
Strong Tunneling and Coulomb Blockade in a Single-Electron Transistor
We have developed a detailed experimental study of a single-electron
transistor in a strong tunneling regime. Although weakened by strong charge
fluctuations, Coulomb effects were found to persist in all samples including
one with the effective conductance 8 times higher than the quantum value (6.45
k). A good agreement between our experimental data and
theoretical results for the strong tunneling limit is found. A reliable
operation of transistors with conductances 3-4 times larger than the quantum
value is demonstrated.Comment: revtex, 4 page
Persistent current noise
We demonstrate that persistent current in meso- and nanorings may fluctuate
down to zero temperature provided the current operator does not commute with
the total Hamiltonian of the system. For a model of a quantum particle on a
ring we explicitly evaluate PC noise power which has a form of sharp peaks
which become broadened for multi-channel rings or in the presence of
dissipation. PC noise can be tuned by an external magnetic flux which is a
fundamental manifestation of quantum coherence in the system.Comment: 4 pages, 1 figur
Coulomb blockade of non-local electron transport in metallic conductors
We consider a metallic wire coupled to two metallic electrodes via two
junctions placed nearby. A bias voltage applied to one of such junctions alters
the electron distribution function in the wire in the vicinity of another
junction thus modifying both its noise and the Coulomb blockade correction to
its conductance. We evaluate such interaction corrections to both local and
non-local conductances demonstrating non-trivial Coulomb anomalies in the
system under consideration. Experiments on non-local electron transport with
Coulomb effects can be conveniently used to test inelastic electron relaxation
in metallic conductors at low temperatures.Comment: Published version. 11 pages, 4 figures. New references added,
discussion and introduction are extended, appendices adde
Evidence for magnetoplasmon character of the cyclotron resonance response of a two-dimensional electron gas
Experimental results on the absolute magneto-transmission of a series of high
density, high mobility GaAs quantum wells are compared with the predictions of
a recent magnetoplasmon theory for values of the filling factor above 2. We
show that the magnetoplasmon picture can explain the non-linear features
observed in the magnetic field evolution of the cyclotron resonance energies
and of the absorption oscillator strength. This provides experimental evidence
that inter Landau level excitations probed by infrared spectroscopy need to be
considered as many body excitations in terms of magnetoplasmons: this is
especially true when interpreting the oscillator strengths of the cyclotron
transitions
Electron transport through interacting quantum dots
We present a detailed theoretical investigation of the effect of Coulomb
interactions on electron transport through quantum dots and double barrier
structures connected to a voltage source via an arbitrary linear impedance.
Combining real time path integral techniques with the scattering matrix
approach we derive the effective action and evaluate the current-voltage
characteristics of quantum dots at sufficiently large conductances. Our
analysis reveals a reach variety of different regimes which we specify in
details for the case of chaotic quantum dots. At sufficiently low energies the
interaction correction to the current depends logarithmically on temperature
and voltage. We identify two different logarithmic regimes with the crossover
between them occurring at energies of order of the inverse dwell time of
electrons in the dot. We also analyze the frequency-dependent shot noise in
chaotic quantum dots and elucidate its direct relation to interaction effects
in mesoscopic electron transport.Comment: 21 pages, 4 figures. References added, discussion slightly extende
Conductance of the Single Electron Transistor for Arbitrary Tunneling Strength
We study the temperature and gate voltage dependence of the conductance of
the single electron transistor focusing on highly conducting devices. Electron
tunneling is treated nonperturbatively by means of path integral Monte Carlo
techniques and the conductance is determined from the Kubo formula. A
regularized singular value decomposition scheme is employed to calculate the
conductance from imaginary time simulation data. Our findings are shown to
bridge between available analytical results in the semiclassical and
perturbative limits and are found to explain recent experimental results in a
regime not accessible by earlier methods.Comment: 4 pages, 2 figure
Penalized maximum likelihood and semiparametric second-order efficiency
We consider the problem of estimation of a shift parameter of an unknown
symmetric function in Gaussian white noise. We introduce a notion of
semiparametric second-order efficiency and propose estimators that are
semiparametrically efficient and second-order efficient in our model. These
estimators are of a penalized maximum likelihood type with an appropriately
chosen penalty. We argue that second-order efficiency is crucial in
semiparametric problems since only the second-order terms in asymptotic
expansion for the risk account for the behavior of the ``nonparametric
component'' of a semiparametric procedure, and they are not dramatically
smaller than the first-order terms.Comment: Published at http://dx.doi.org/10.1214/009053605000000895 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
- …