689 research outputs found
Transport through molecular junctions with a nonequilibrium phonon population
The calculation of the nonlinear conductance of a single-molecule junction is
revisited. The self energy on the junction resulting from the electron-phonon
interaction has at low temperatures logarithmic singularities (in the real
part) and discontinuities (in the imaginary one) at the frequencies
corresponding to the opening of the inelastic channels. These singularities
generate discontinuities and logarithmic divergences (as a function of the bias
voltage) in the low-temperature differential conductance around the inelastic
thresholds. The self energy also depends on the population of the vibrational
modes. The case of a vibrating free junction (not coupled to a thermal bath),
where the phonon population is determined by the bias voltage is examined. We
compare the resulting zero-temperature differential conductance with the one
obtained for equilibrated phonons, and find that the difference is larger the
larger is the bare transmission of the junction and the product of the electron
dwell time on the junction with the phonon frequency.Comment: 4 page
The noise spectra of a biased quantum dot
The noise spectra associated with correlations of the current through a
single level quantum dot, and with the charge fluctuations on the dot, are
calculated for a finite bias voltage. The results turn out to be sensitive to
the asymmetry of the dot's coupling to the two leads. At zero temperature, both
spectra exhibit two or four steps (as a function of the frequency), depending
on whether the resonant level lies outside or within the range between the
chemical potentials on the two leads. In addition, the low frequency shot-noise
exhibits dips in the charge noise and dips, peaks, and discontinuities in the
derivative of the current noise. In spite of some smearing, several of these
features persist at finite temperatures, where a dip can also turn into a peak
Transmission of two interacting electrons
The transmission of two electrons through a region where they interact is
found to be enhanced by a renormalization of the repulsive interaction. For a
specific example of the single-particle Hamiltonian, which includes a strongly
attractive potential, the renormalized interaction becomes attractive, and the
transmission has a pronounced maximum as function of the depth of the
single-electron attractive potential. The results apply directly to a simple
model of scattering of two interacting electrons by a quantum dot.Comment: 12 pages, 2 figure
Quantized charge pumping by surface acoustic waves in ballistic quasi-1D channels
Adiabatic pumping of electrons induced by surface acoustic waves (SAWs) in a
ballistic quasi-1D quantum channel is considered using an exactly solvable
tight-binding model for non-interacting electrons. The single-electron degrees
of freedom, responsible for acoustoelectric current quantization, are related
to the transmission resonances. We study the influence of experimentally
controllable parameters (SAW power, gate voltage, source-drain bias, amplitude
and phase of a secondary SAW beam) on the plateau-like structure of the
acoustoelectric current. The results are consistent with existing experimental
observations.Comment: 11 pages, 8 figure
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