Quantum behaviour in nano-mechanical systems
Author(s)
Tahir, Muhammed
Type
Thesis
Abstract
The emerging field of nano-electro-mechanical systems (NEMS), in which the single
mode of a nanomechanical oscillator plays the role of an active device, is receiving much
attention due to its technological importance. The characteristic component that gives the
name to these devices is an oscillator of nanometer size coupled to the electrons on the dot
that transfer electrons one-by-one between a source and a drain lead. From a fundamental
point of view, it is important to understand the interplay between the electronic transport
and the nanomechanical motion of the oscillator quantum mechanically.
This thesis contains the description and analysis of the dynamics of a nanomechanical
oscillator coupled to a resonant tunnel junction (RTJ) and its realization as a
shuttle device. The models we consider describe both the mechanical and electrical degrees
of freedom quantum mechanically; Firstly, a RTJ coupled to a nanomechanical oscillator.
Secondly, we report a first complete quantum mechanical analysis of a charge shuttle. We
introduce a new non-perturbative quantum mechanical description for the strong interaction
of both the electrical and the mechanical object, which is beyond the existing experiments.
We describe a nonequilibrium Green’s function formalism: a well suited technique to treat
this kind of far from equilibrium systems, which can deal with very small to very large
applied bias. The numerical implementation of these models are discussed in detail, and
the transient and the steady state behavior of the system is also considered here for the
quantum dynamics of the oscillator as a function of time. This will provide useful insight
for the design of experiments aimed at studying the quantum behavior of an oscillator.
mode of a nanomechanical oscillator plays the role of an active device, is receiving much
attention due to its technological importance. The characteristic component that gives the
name to these devices is an oscillator of nanometer size coupled to the electrons on the dot
that transfer electrons one-by-one between a source and a drain lead. From a fundamental
point of view, it is important to understand the interplay between the electronic transport
and the nanomechanical motion of the oscillator quantum mechanically.
This thesis contains the description and analysis of the dynamics of a nanomechanical
oscillator coupled to a resonant tunnel junction (RTJ) and its realization as a
shuttle device. The models we consider describe both the mechanical and electrical degrees
of freedom quantum mechanically; Firstly, a RTJ coupled to a nanomechanical oscillator.
Secondly, we report a first complete quantum mechanical analysis of a charge shuttle. We
introduce a new non-perturbative quantum mechanical description for the strong interaction
of both the electrical and the mechanical object, which is beyond the existing experiments.
We describe a nonequilibrium Green’s function formalism: a well suited technique to treat
this kind of far from equilibrium systems, which can deal with very small to very large
applied bias. The numerical implementation of these models are discussed in detail, and
the transient and the steady state behavior of the system is also considered here for the
quantum dynamics of the oscillator as a function of time. This will provide useful insight
for the design of experiments aimed at studying the quantum behavior of an oscillator.
Date Issued
2010-03
Date Awarded
2010-06
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Sponsor
Pakistan Higher Education Commission (HEC)
Creator
Tahir, Muhammed
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)