Excitation dynamics of strongly dissipative quantum systems

Research output: ThesisDoctoral Thesis


Strong coupling between a quantum system and its many-body environment is becoming
an increasingly important topic for many branches of physics. Numerous systems of experimental and technological relevance demonstrate strong system-environment coupling,
leading to complex dynamical behaviour. This thesis is concerned with two particular examples of such systems, namely quantum dots (QDs) and excitonic energy transfer (EET)
in molecular systems.
Traditional quantum optics treatments are often insucient to describe the transient,
steady state, and optical properties of QDs due to system-environment correlations. In
contrast, we present a modified theory of quantum optics capable of capturing the influence of a thermal environment on the behaviour of QDs. Using this framework we demonstrate a striking departure of the emission spectra and photon measurement statistics of
a classically driven QD when compared to an analogous atomic system. Furthermore, in
contradiction to accepted notions of decoherence and dissipation, we show that the interaction between a QD and its thermal environment induces non-classical light-matter
correlations in an otherwise semi-classical regime of cavity quantum electrodynamics.
Away from QDs, we develop the reaction coordinate (RC) formalism to describe the
dynamics of a system coupled to a low frequency environment — a regime important to
EET systems. We do so by identifying and incorporating important environmental degrees
of freedom into an enlarged system Hamiltonian. Uniquely, this approach gives insight
directly into the dynamical evolution of the environment and correlations accumulated
between the system and environment. Furthermore, it is demonstrated that these correlations persist into the steady state, generating non-canonical equilibrium states of the
system and environment.
We then apply the RC model to describe EET in a molecular dimer, highlighting
the eect that under- and over-damped environments have on the excitation dynamics.
In doing so, we show interactions between the dimer and a structured environment can
significantly enhance the energy transfer rate.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Imperial College London
  • Nazir, Ahsan, Supervisor
  • Lovett, Brendon W., Supervisor, External person
Award date1 Sept 2015
Publication statusPublished - 2015


Dive into the research topics of 'Excitation dynamics of strongly dissipative quantum systems'. Together they form a unique fingerprint.

Cite this