1,522 research outputs found
Suppression of stochastic fluctuations of suspended nanowires by temperature-induced single-electron tunnelling
We investigate theoretically the electromechanical properties of freely
suspended nanowires that are in tunnelling contact with the tip of a scanning
tunnelling microscope (STM) and two supporting metallic leads. The aim of our
analysis is to characterize the fluctuations of the dynamical variables of the
nanowire when a temperature drop is mantained between the STM tip and the
leads, which are all assumed to be electrically grounded. By solving a quantum
master equation that describes the coupled dynamics of electronic and
mechanical degrees of freedom we find that the stationary state of the
mechanical oscillator has a Gaussian character, but that the amplitude of its
root-mean square center-of-mass fluctuations is smaller than would be expected
if the system were coupled only to the leads at thermal equilibrium.Comment: Published versio
Vibrational Instability due to Coherent Tunneling of Electrons
Effects of a coupling between the mechanical vibrations of a quantum dot
placed between the two leads of a single electron transistor and coherent
tunneling of electrons through a single level in the dot has been studied. We
have found that for bias voltages exceeding a certain critical value a
dynamical instability occurs and mechanical vibrations of the dot develop into
a stable limit cycle. The current-voltage characteristics for such a transistor
were calculated and they seem to be in a reasonably good agreement with recent
experimental results for the single -molecule transistor by Park et
al.(Nature {\bf 407,} (2000) 57).Comment: 5 pages, 3 figure
Resonant microwave properties of a voltage-biased single-Cooper-pair transistor
We consider the microwave dynamics and transport properties of a
voltage-biased single-Cooper-pair transistor. The dynamics is shown to be
strongly affected by interference between multiple microwave-induced
inter-level transitions. As a result the magnitude and direction of the dc
Josephson current are extremely sensitive to small variations of the bias
voltage and to changes in the frequency of the microwave field.Comment: 6 pages, 4 figure
Electronic Aharonov-Bohm Effect Induced by Quantum Vibrations
Mechanical displacements of a nanoelectromechanical system (NEMS) shift the
electron trajectories and hence perturb phase coherent charge transport through
the device. We show theoretically that in the presence of a magnetic feld such
quantum-coherent displacements may give rise to an Aharonov-Bohm-type of
effect. In particular, we demonstrate that quantum vibrations of a suspended
carbon nanotube result in a positive nanotube magnetoresistance, which
decreases slowly with the increase of temperature. This effect may enable one
to detect quantum displacement fluctuations of a nanomechanical device.Comment: 4 pages, 3 figure
Spintromechanics of a Magnetic Nanoshuttle
We investigate theoretically the prospects for using a magnetic
nanoelectromechanical single-electron tunneling (NEM-SET) device as an
electronic spin filter. We find that strong magnetic exchange forces on the net
spin of the mobile central dot of the NEM-SET structure lead to spin-dependent
mechanical displacements ("spin polarons"), which give rise to vastly different
tunnelling probabilities for electrons of different spin. The resulting spin
polarization of the current can be controlled by bias and gate voltages and be
very close to 100% at voltages and temperatures below a characteristic
correlation energy set by the sum of the polaronic and Coulomb blockade
energies.Comment: Accepted for publication as a Rapid Communication in Phys. Rev. B and
selected as an "Editors' Suggestion" paper. This version has minor
modifications compared to arXiv:1205.2979, which it replace
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