86 research outputs found
Acoustic transport of electrons in parallel quantum wires
Over the last few years we have developed a new method to control single-electrons by isolating and moving them through a submicron width channel formed in a GaAs/AlGaAs heterostructure using a surface acoustic wave. The acoustic wave acts to push electrons through the depleted submicron channel in packets each containing an integer number of electrons. Our primary motivation for studying this system has been to develop a new standard of dc current for metrological purposes, but our recent focus has widened to investigate the possibility of single-photon emission. Here we show new experimental results which demonstrate acoustoelectric current flow in adjacent 1D wires. These results have relevance both to the use of the system in a single-photon emission scheme, as well as in the creation of a proposed acoustoelectric quantum computer
Surface Acoustic Wave Single-Electron Interferometry
We propose an experiment to observe interference of a single electron as it
is transported along two parallel quasi-one-dimensional channels trapped in a
single minimum of a travelling periodic electric field. The experimental device
is a modification of the surface acoustic wave (SAW) based quantum processor.
Interference is achieved by creating a superposition of spatial wavefunctions
between the two channels and inducing a relative phase shift via either a
transverse electric field or a magnetic field. The interference can be used to
estimate the decoherence time of an electron in this type of solid-state
device
Quantized adiabatic charge pumping and resonant transmission
Adiabatically pumped charge, carried by non-interacting electrons through a
quantum dot in a turnstile geometry, is studied as function of the strength of
the two modulating potentials (related to the conductances of the two
point-contacts to the leads) and of the phase shift between them. It is shown
that the magnitude and sign of the pumped charge are determined by the relative
position and orientation of the closed contour traversed by the system in the
parameter plane, and the transmission peaks (or resonances) in that plane.
Integer values (in units of the electronic charge ) of the pumped charge
(per modulation period) are achieved when a transmission peak falls inside the
pumping contour. The integer value is given by the winding number of the
pumping contour: double winding in the same direction gives a charge of 2,
while winding around two opposite branches of the transmission peaks or winding
in opposite directions can give a charge close to zero.Comment: 7 pages, 12 figure
Charge Pumping in Carbon Nanotubes
We demonstrate charge pumping in semiconducting carbon nanotubes by a
traveling potential wave. From the observation of pumping in the nanotube
insulating state we deduce that transport occurs by packets of charge being
carried along by the wave. By tuning the potential of a side gate, transport of
either electron or hole packets can be realized. Prospects for the realization
of nanotube based single-electron pumps are discussed
AC Driven Jumps Distribution on a Periodic Substrate
A driven Brownian particle (e.g. an adatom on a surface) diffusing on a
low-viscosity, periodic substrate may execute multiple jumps. In the presence
of an additional periodic drive, the jump lengths and time durations become
statistically modulated according to a syncronyzation mechanism reminiscent of
asymmetric stochastic resonance. Here, too, bistability plays a key role, but
in a dynamical sense, inasmuch as a particle switches between locked and
running states.Comment: 4 pages, 4 figures, RevTeX, to be published in Surface Science
Letter
Quantized charge transport through a static quantum dot using a surface acoustic wave
We present a detailed study of the surface acoustic wave mediated quantized
transport of electrons through a split gate device containing an impurity
potential defined quantum dot within the split gate channel. A new regime of
quantized transport is observed at low RF powers where the surface acoustic
wave amplitude is comparable to the quantum dot charging energy. In this regime
resonant transport through the single-electron dot state occurs which we
interpret as turnstile-like operation in which the traveling wave amplitude
modulates the entrance and exit barriers of the quantum dot in a cyclic fashion
at GHz frequencies. For high RF powers, where the amplitude of the surface
acoustic wave is much larger than the quantum dot energies, the quantized
acoustoelectric current transport shows behavior consistent with previously
reported results. However, in this regime, the number of quantized current
plateaus observed and the plateau widths are determined by the properties of
the quantum dot, demonstrating that the microscopic detail of the potential
landscape in the split gate channel has a profound influence on the quantized
acoustoelectric current transport.Comment: 9 page
Quantized Adiabatic Charge Transport in a Carbon Nanotube
The coupling of a metallic Carbon nanotube to a surface acoustic wave (SAW)
is proposed as a vehicle to realize quantized adiabatic charge transport in a
Luttinger liquid system. We demonstrate that electron backscattering by a
periodic SAW potential, which results in miniband formation, can be achieved at
energies near the Fermi level. Electron interaction, treated in a Luttinger
liquid framework, is shown to enhance minigaps and thereby improve current
quantization. Quantized SAW induced current, as a function of electron density,
changes sign at half-filling.Comment: 5 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
Non-adiabaticity and single-electron transport driven by surface acoustic waves
Single-electron transport driven by surface acoustic waves (SAW) through a
narrow constriction, formed in two-dimensional electron gas, is studied
theoretically. Due to long-range Coulomb interaction, the tunneling coupling
between the electron gas and the moving minimum of the SAW-induced potential
rapidly decays with time. As a result, nonadiabaticiy sets a limit for the
accuracy of the quantization of acoustoelectric current
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