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Electronic Control of Flexural Nanowire Vibrations

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.
Parts of work
Paper I Self-organization of irregular nanoelectromechanical vibrations in multimode shuttle structures, L. M. Jonsson, F. Santandrea, L. Y. Gorelik, R. I. Shekhter and M. Jonson, Phys. Rev. Lett. 100, 186802 (2008). ::doi::10.1103/PhysRevLett.100.186802
 
Paper II Selective excitations of transverse vibrational modes of a carbon nanotube through a “shuttle-like” electromechanical instability F. Santandrea, Physics Research International vol. 2010, 493478. ::doi::10.1155/2010/493478
 
Paper III Cooling of nanomechanical resonators by thermally activated single-electron transport F. Santandrea, L. Y. Gorelik, R. I. Shekhter and M. Jonson, Phys. Rev. Lett. 106, 186803 (2011). ::doi::10.1103/PhysRevLett.106.186803
 
Paper IV Suppression of stochastic fluctuations of suspended nanowires by temperature-induced electronic tunneling, F. Santandrea, L. Y. Gorelik, R. I. Shekhter and M. Jonson. Unpublished manuscript.
 
Degree
Doctor of Philosophy
University
Göteborgs universitet. Naturvetenskapliga fakulteten
Institution
Department of Physics ; Institutionen för fysik
Disputation
Torsdagen den 9 juni 2011, kl. 10.00, Kollektorn, Institutionen för mikroteknologi och nanovetenskap (Chalmers), Kemivägen 9, Göteborg
Date of defence
2011-06-09
E-mail
fabio.santandrea@physics.gu.se
menippo137@gmail.com
URI
http://hdl.handle.net/2077/25321
Collections
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • Doctoral Theses from University of Gothenburg / Doktorsavhandlingar från Göteborgs universitet
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Thesis (1.437Mb)
Abstract (38.64Kb)
Date
2011-05-19
Author
Santandrea, Fabio
Keywords
Nanoelectromechanical systems
Carbon nanotubes
Coulomb blockade
Shuttle instability
Ground-state cooling
Publication type
Doctoral thesis
ISBN
978-91-633-5863-0
Language
eng
Metadata
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