9,838 research outputs found
Statistics of heat exchange between two resistors
We study energy flow between two resistors coupled by an arbitrary linear and
lossless electric circuit. We show that the fluctuations of energy transferred
between the resistors are determined by random scattering of photons on an
effective barrier with frequency dependent transmission probability
. We express the latter in terms of the circuit parameters. Our
results are valid in both quantum and classical regimes and for non-equilibrium
electron distribution functions in the resistors.Comment: 7 pages, 4 figures. Published version. New figures added, discussion
extende
Effect of Nyquist Noise on the Nyquist Dephasing Rate in 2d Electron Systems
We measure the effect of externally applied broadband Nyquist noise on the
intrinsic Nyquist dephasing rate of electrons in a two-dimensional electron gas
at low temperatures. Within the measurement error, the phase coherence time is
unaffected by the externally applied Nyquist noise, including applied noise
temperatures of up to 300 K. The amplitude of the applied Nyquist noise from
100 MHz to 10 GHz is quantitatively determined in the same experiment using a
microwave network analyzer.Comment: 5 pages, 4 figures. Author affiliation clarified; acknowledgements
modified. Replacement reason clarifie
Aharonov-Bohm ring with fluctuating flux
We consider a non-interacting system of electrons on a clean one-channel
Aharonov-Bohm ring which is threaded by a fluctuating magnetic flux. The flux
derives from a Caldeira-Leggett bath of harmonic oscillators. We address the
influence of the bath on the following properties: one- and two-particle
Green's functions, dephasing, persistent current and visibility of the
Aharonov-Bohm effect in cotunneling transport through the ring. For the bath
spectra considered here (including Nyquist noise of an external coil), we find
no dephasing in the linear transport regime at zero temperature.
PACS numbers: 73.23.-b, 73.23.Hk, 73.23.Ra, 03.65.YzComment: 17 pages, 8 figures. To be published in PRB. New version contains
minor corrections and additional discussion suggested by referee. A simple
introduction to the basics of dephasing can be found at
http://iff.physik.unibas.ch/~florian/dephasing/dephasing.htm
Coulomb blockade in one-dimensional arrays of high conductance tunnel junctions
Properties of one-dimensional (1D) arrays of low Ohmic tunnel junctions (i.e.
junctions with resistances comparable to, or less than, the quantum resistance
k) have been studied experimentally
and theoretically. Our experimental data demonstrate that -- in agreement with
previous results on single- and double-junction systems -- Coulomb blockade
effects survive even in the strong tunneling regime and are still clearly
visible for junction resistances as low as 1 k. We have developed a
quasiclassical theory of electron transport in junction arrays in the strong
tunneling regime. Good agreement between the predictions of this theory and the
experimental data has been observed. We also show that, due to both heating
effects and a relatively large correction to the linear relation between the
half-width of the conductance dip around zero bias voltage, , and the
measured electronic temperature, such arrays are inferior to those
conventionally used in the Coulomb Blockade Thermometry (CBT). Still, the
desired correction to the half-width, , can be determined
rather easily and it is proportional to the magnitude of the conductance dip
around zero bias voltage, . The constant of proportionality is a
function of the ratio of the junction and quantum resistances, ,
and it is a pure strong tunneling effect.Comment: LaTeX file + five postscript figure
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
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
Disorder-induced pseudodiffusive transport in graphene nanoribbons.
We study the transition from ballistic to diffusive and localized transport in graphene nanoribbons in the presence of binary disorder, which can be generated by chemical adsorbates or substitutional doping. We show that the interplay between the induced average doping (arising from the nonzero average of the disorder) and impurity scattering modifies the traditional picture of phase-coherent transport. Close to the Dirac point, intrinsic evanescent modes produced by the impurities dominate transport at short lengths giving rise to a regime analogous to pseudodiffusive transport in clean graphene, but without the requirement of heavily doped contacts. This intrinsic pseudodiffusive regime precedes the traditional ballistic, diffusive, and localized regimes. The last two regimes exhibit a strongly modified effective number of propagating modes and a mean free path which becomes anomalously large close to the Dirac point
Dephasing at Low Temperatures
We discuss the significance and the calculation of dephasing at low
temperatures. The particle is moving diffusively due to a static disorder
configuration, while the interference between classical paths is suppressed due
to the interaction with a dynamical environment. At high temperatures we may
use the `white noise approximation' (WNA), while at low temperatures we
distinguish the contribution of `zero point fluctuations' (ZPF) from the
`thermal noise contribution' (TNC). We study the limitations of the above
semiclassical approach and suggest the required modifications. In particular we
find that the ZPF contribution becomes irrelevant for thermal motion.Comment: 4 pages, 1 figure, clearer presentatio
Weak localization, Aharonov-Bohm oscillations and decoherence in arrays of quantum dots
Combining scattering matrix theory with non-linear -model and Keldysh
technique we develop a unified theoretical approach enabling one to
non-perturbatively study the effect of electron-electron interactions on weak
localization and Aharonov-Bohm oscillations in arbitrary arrays of quantum
dots. Our model embraces (i) weakly disordered conductors (ii) strongly
disordered conductors and (iii) metallic quantum dots. In all these cases at the electron decoherence time is found to saturate to a finite value
determined by the universal formula which agrees quantitatively with numerous
experimental results. Our analysis provides overwhelming evidence in favor of
electron-electron interactions as a universal mechanism for zero temperature
electron decoherence in disordered conductors.Comment: 19 pages, 13 figures, invited paper, published in a special issue of
Fiz. Nizk. Temp. (Kharkov) dedicated to Prof. Igor Kuli
Interaction-Induced Quantum Dephasing in Mesoscopic Rings
Combining nonperturbative techniques with Monte Carlo simulations we
demonstrate that quantum coherence effects for a particle on a ring are
suppressed beyond a finite length even at zero temperature if the
particle is coupled to a diffusive electron gas by means of long range Coulomb
interaction. This length is consistent with derived from
weak-localization-type of analysis.Comment: 4 revtex pages, 2 figure
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