The outline of this work will be as follows: in chapter 1, after a brief
overview of the systems studied and a preview of the results obtained, we
will introduce the general models and methods we are going to use to tackle
the systems considered, hopefully providing enough theory to understand our
later extensive treatment, without entering in too much detail in the widely
studied general theories of our models. In chapter 2 we will show our first
application: the description of a spin-sensitive dissipation channel compatible
with the experimental findings of an atomic force microscopy experiment. We
will describe in some detail the experiment and the system under study and
why some direct approaches are unable to account for the observed effect; we
will then specialize the previously described path integral technique to obtain
a numerical description of the system, highlighting our proposed dissipation
mechanism. In chapter 3 we will consider electron current pumping in a threesite
system and how it can be affected by the presence of an environment.
We will first obtain and solve a simple equation for the isolated system, then
couple a bath to this and specialize the master equation theory to obtain
an analytical result for the system in presence of an environment, observing
some interesting changes it its behavior. The experimental feasibility of
the proposed setup will be explored. Finally, in chapter 4 we will briefly
present another model for the description of dissipative systems which has
been investigated but, for now, is not complete enough to produce interesting
results: inspired from another atomic force microscopy experiment where
frictional effects of hydrogen atoms on a surface are observed, we will try to
investigate the possibility of inherently quantum effects in a similar system,
where a light particle is coupled to other heavier atoms, treated classically.
We will propose a model and a technique for its simulation, though this will
prove too computationally demanding to be of practical use.
