302 research outputs found
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
Spintronics of a Nanoelectromechanical Shuttle
We consider effects of the spin degree of freedom on the nanomechanics of a
single-electron transistor (SET) containing a nanometer-sized metallic cluster
suspended between two magnetic leads. It is shown that in such a
nanoelectromechanical SET(NEM-SET) the onset of an electromechanical
instability leading to cluster vibrations and "shuttle" transport of electrons
between the leads can be controlled by an external magnetic field. Different
stable regimes of this spintronic NEM-SET operation are analyzed. Two different
scenarios for the onset of shuttle vibrations are found.Comment: 4 pages, 3 figure
Quantum Shuttle Phenomena in a Nanoelectromechanical Single-Electron Transistor
An analytical analysis of quantum shuttle phenomena in a
nanoelectromechanical single-electron transistor has been performed in the
realistic case, when the electron tunnelling length is much greater than the
amplitude of the zero point oscillations of the central island. It is shown
that when the dissipation is below a certain threshold value, the vibrational
ground state of the central island is unstable. The steady-state into which
this instability develops is studied. It is found that if the electric field
between the leads is much greater than a characteristic value , the quasiclassical shuttle picture is recovered, while if a new quantum regime of shuttle vibrations occurs. We show
that in the latter regime small quantum fluctuations result in large (i.e.
finite in the limit ) shuttle vibrations.Comment: 5 pages, 1 figur
Electromechanical instability in suspended carbon nanotubes
We have theoretically investigated electromechanical properties of freely
suspended carbon nanotubes when a current is injected into the tubes using a
scanning tunneling microscope. We show that a shuttle-like electromechanical
instability can occur if the bias voltage exceeds a dissipation-dependent
threshold value. An instability results in large amplitude vibrations of the
carbon nanotube bending mode, which modify the current-voltage characteristics
of the system
Multiscale Modeling of a Nanoelectromechanical Shuttle
In this article, we report a theoretical analysis of a nanoelectromechanical
shuttle based on a multiscale model that combines microscopic electronic
structure data with macroscopic dynamics. The microscopic part utilizes a
(static) density functional description to obtain the energy levels and
orbitals of the shuttling particle together with the forces acting on the
particle. The macroscopic part combines stochastic charge dynamics that
incorporates the microscopically evaluated tunneling rates with a Newtonian
dynamics.
We have applied the multiscale model to describe the shuttling of a single
copper atom between two gold-like jellium electrodes. We find that energy
spectrum and particle surface interaction greatly influence shuttling dynamics;
in the specific example that we studied the shuttling is found to involve only
charge states Q=0 and Q=+e. The system is found to exhibit two quasi-stable
shuttling modes, a fundamental one and an excited one with a larger amplitude
of mechanical motion, with random transitions between them.Comment: 9 pages, 9 figure
Low frequency current noise of the single-electron shuttle
Coupling between electronic and mechanical degrees of freedom in a single
electron shuttle system can cause a mechanical instability leading to shuttle
transport of electrons between external leads. We predict that the resulting
low frequency current noise can be enhanced due to amplitude fluctuations of
the shuttle oscillations. Moreover, at the onset of mechanical instability a
pronounced peak in the low frequency noise is expected.Comment: 14 pages, 3 figures, 1 tabl
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