| 1. |
- Gorelik, Leonid, 1952, et al.
(författare)
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Suppression of thermal fluctuations of nanomechanical resonator (ground state cooling) by thermally activated electronic flow
- 2011
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Ingår i: 21st International Conference on Noise and Fluctuations, ICNF 2011; Toronto, ON; 12 June 2011 through 16 June 2011. - 9781457701924 ; , s. 223-226
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Konferensbidrag (refereegranskat)abstract
- We consider a doubly clamped suspended metallic carbon nanotube in which extra charge is injected from the tipof a scanning tunneling microscopy (STM). Our analysis shows that the quantum superposition between the different inelastic electronic tunneling paths can be controlled by the bias voltage. In particular, we find that below Coulomb blockade threshold the vibron emission induced by thermally activated electron transportation can be significantly reduced in comparison to the vibron absorption. As a consequence a net suppression of the thermal fluctuations ("cooling") of the vibrational degrees of freedom can be achieved. © 2011 IEEE.
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| 2. |
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| 3. |
- Jonsson, Magnus, 1979, et al.
(författare)
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Self-organization of irregular nanoelectromechanical vibrations in multimode shuttle structures
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:18
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Tidskriftsartikel (refereegranskat)abstract
- We investigate theoretically multimode electromechanical "shuttle" instabilities in dc voltage-biased nanoelectromechanical single-electron tunneling devices. We show that initially irregular (quasiperiodic) oscillations that occur as a result of the simultaneous self-excitation of several mechanical modes with incommensurable frequencies self-organize into periodic oscillations with a frequency corresponding to the eigenfrequency of one of the unstable modes. This effect demonstrates that a local probe can selectively excite global vibrations of extended objects.
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| 4. |
- Santandrea, Fabio, 1981, et al.
(författare)
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Cooling of Nanomechanical Resonators by Thermally Activated Single-Electron Transport
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:18
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Tidskriftsartikel (refereegranskat)abstract
- We show that the vibrations of a nanomechanical resonator can be cooled to near its quantum ground state by tunneling injection of electrons from a scanning tunneling microscope tip. The interplay between two mechanisms for coupling the electronic and mechanical degrees of freedom results in a bias-voltage-dependent difference between the probability amplitudes for vibron emission and absorption during tunneling. For a bias voltage just below the Coulomb blockade threshold, we find that absorption dominates, which leads to cooling corresponding to an average vibron population of the fundamental bending mode of 0.2.
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| 5. |
- Santandrea, Fabio, 1981
(författare)
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Electromechanical Instability in Suspended Nanowire-Based NEMS
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- "Nanoelectromechanical systems'' (NEMS) are a class of nanometer-sized mechanical structures coupled to electronic device of comparable dimensions. Their peculiar features make them interesting both from the technological and fundamental research viewpoints. The dynamics of the movable part of these devices is affected on the conditions at which electric charge is transferred across them and vice versa, therefore NEMS offer the ideal playground to investigate the physical effects which originate from coupling mechanical and electronic degrees of freedom at the nanoscale. In this thesis I describe the properties of one of such effects, i.e. the electromechanical instability that can take place in a DC-biased suspended doubly clamped carbon nanotube in which extra charge is locally injected through the tip of a scanning tunneling microscope (STM). The sequence of tunneling events makes the charge state of the nanotube vary in time and accordingly the force exerted on it by the electrostatic field (which is created by the bias voltage) changes in time and can induce mechanical vibrations in the nanotube. Furthermore, the probability of electron tunneling between the tip of the STM and the nanotube depends on the distance between them, hence a coupling between the mechanical and electronic degrees of freedom of the system is established. The analysis described in this thesis indicates that if the energy pumped into the nanotube by the electrostatic field is sufficient to overcome the energy lost because of dissipative processes, the static equilibrium configuration of the nanotube becomes unstable. The onset of the electromechanical instability implies that initially quasi-periodic oscillations (to which all the unstable modes contribute) self-organize into periodic oscillations with a frequency corresponding to the eigenfrequency of one of the unstable modes. Furthermore, the results presented here suggests the possibility to selectively excite the transverse vibrational modes of the nanotube by optimizing their coupling to the electrostatic field through the positioning of the STM tip. This effect could provide the basic physical mechanism for a feasible procedure to control the dynamics of NEMS.
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| 6. |
- Santandrea, Fabio, 1981
(författare)
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Electronic Control of Flexural Nanowire Vibrations
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- “Nanoelectromechanical systems” (NEMS) are nanometer-sized mechanical structures coupled to electronic devices of comparable size. The coupling between mechanical and electronic degrees of freedom, combined with their mesoscopic size, provide these systemswith some unique properties that make them interesting from both the fundamental and technological point of view. In this thesis, we present theoretical work about a specific kind of NEMS, that is a suspended doubly clamped carbon nanotube in which extra charge is locally injected through the DC voltage-biased tip of a scanning tunneling microscope (STM). The analysis presented here indicates that, in the classical regime, under the conditions of weak dissipation or sufficiently strong electromechanical coupling, the equilibrium configuration of the suspended nanotube becomes unstable and the system evolves towards a state of self-sustained periodic oscillations that is reminescent of the single-electron “shuttle” regime in Coulomb blockade nanostructures. Furthermore, combining the conditions for the onset of the electromechanical instability with the local character of the charge injection provided by the STM, it seems possible to generate a selective excitation of the bending vibrational modes of the nanotube. Instead of pumping energy into the suspended nanotube, the electromechanical coupling can be also exploited to remove energy from it. Even though the tunneling electrons represent a strongly nonequilibrium environment interacting with the mechanical subsystem, the analysis presented in this thesis shows that the dynamics of the nanotube in the regime ofweak coupling is formally equivalent to that one of a quantum harmonic oscillator coupled to an equilibrium thermal bath characterized by an effective temperature that can be much lower than the environmental (i.e. thermodynamic) temperature. This nonequilibrium cooling effect studied here has an intrinsic quantum mechanical nature, since it is based on the (bias voltage controlled-) destructive interference between the probability amplitudes associated to those inelastic tunneling processes characterized by the emission of quantized vibrational excitations. When the transport of charge is thermally activated, this mechanism provides a simple procedure to drive the oscillating nanotube to nearly its quantum ground state.
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| 7. |
- Santandrea, Fabio, 1981
(författare)
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Selective Excitations of Transverse Vibrational Modes of a Carbon Nanotube through a "Shuttle-Like" Electromechanical Instability
- 2010
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Ingår i: Physics Research International. - 2090-2220. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- We study the dynamics of transverse oscillations of a suspended carbon nanotube into which electron current is injected from the tip of a scanning tunneling microscope (STM). In this case the correlations between the displacement of the nanotube and its charge state, determined by the position-dependent electron tunneling rate, can lead to a “shuttle-like” instability for the transverse vibrational modes. We find that selective excitation of a specific mode can be achieved by an accurate positioning of the STM tip. This result suggests a feasible way to control the dynamics of this nano-electromechanical system (NEMS) based on the “shuttle instability.”
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| 8. |
- Santandrea, Fabio, 1981, et al.
(författare)
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Suppression of the stochastic fluctuations of suspended nanowires by temperature-induced single-electron tunneling
- 2011
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically investigate the electromechanical properties of freely suspended nanowires that are in tunneling contact with the tip of a scanning tunneling 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 maintained 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 found 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.
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| 9. |
- Shekhter, Robert I., 1947, et al.
(författare)
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Nonequilibrium and quantum coherent phenomena in the electromechanics of suspended nanowires
- 2009
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1090-6517 .- 1063-777X. ; 35:8
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Forskningsöversikt (refereegranskat)abstract
- Strong coupling between electronic and mechanical degrees of freedom is a basic requirement for the operation of any nanoelectromechanical device. In this Review we consider such devices and in particular investigate the properties of small tunnel-junction nanostructures that contain a movable element in the form of a suspended nanowire. In these systems, electrical currents and charge can be concentrated to small spatial volumes resulting in strong coupling between the mechanics and the charge transport. As a result, a variety of mesoscopic phenomena appear, which can be used for the transduction of electrical currents into mechanical operation. Here we will in particular consider nanoelectromechanical dynamics far from equilibrium and the effect of quantum coherence in both the electronic and mechanical degrees of freedom in the context of both normal and superconducting nanostructures.
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