Klauser, Daniel Joseph. Hyperfine interaction and spin decoherence in quantum dots. 2008, PhD Thesis, University of Basel, Faculty of Science.
Official URL: http://edoc.unibas.ch/diss/DissB_8302
sites of the underlying cristal lattice, the electron spin also interacts with many
nuclei, in sharp contrast to an electron spin in an atom, which only interacts
with a single nucleus.
In this thesis we address several aspects of hyperfine interaction and decoherence
in quantum dots. First, we analyze some aspects of the decoherence
that arises from the hyperfine interaction. In the case of driven single-spin
oscillations we show that hyperfine interaction leads to a universal phase shift
and a power-law decay. Both of these effects have been confirmed experimentally.
We also find a universal phase shift and a power-law decay for the case
of two electron spins in a double quantum dot in the subspace with total spin
zero along the quantization axis. The appearance of the these effects both
in single and in double quantum dots is a consequence of the non-Markovian
nature of the nuclear spin bath.
Since the main effect of hyperfine-induced decoherence can be attributed to
the uncertainty in the Overhauser field, the effective magnetic field generated
by the nuclei at the position of the electron, one strategy to reduce decoherence
is to prepare the nuclei in a state with a narrow Overhauser field distribution,
i.e., to narrow the nuclear spin state. We propose a method to measure the
Overhauser field using the dynamics of the electron spins as a probe. More
specifically, we propose to narrow the nuclear spin state by monitoring Rabi
oscillations in a double quantum dot.
Hyperfine interaction not only leads to decoherence of the electron spin
state, it also provides a mechanism for interaction between the nuclei in the
quantum dot. We study the dynamics of the Overhauser field under the mutual
interaction between nuclear spins that is mediated by the electron via the
hyperfine interaction. At high magnetic fields we find an incomplete decay of
the Overhauser field. We further show that the decay of the Overhauser field
can be suppressed by measuring the Overhauser field, a clear manifestation of
the quantum Zeno effect.
|Committee Members:||Imamoğlu, Atac|
|Faculties and Departments:||05 Faculty of Science > Departement Physik > Physik > Theoretische Physik Mesoscopics (Loss)|
|Bibsysno:||Link to catalogue|
|Number of Pages:||96|
|Last Modified:||30 Jun 2016 10:41|
|Deposited On:||13 Feb 2009 16:28|
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