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Title: Fullerene based systems for optical spin readout
Author: Rahman, Rizvi
ISNI:       0000 0004 2728 2546
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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Optical spin readout (OSR) in fullerene-based systems has the potential to solve the spin readout and scalability challenges in solid-state quantum information processing. While the rich variety of chemical groups that can be linked (covalently or not) to the fullerenes opens the possibility of making large and controlled arrays of qubits, optical methods can be used to measure EPR down to a single spin thanks to the large energy of optical photons compared to the microwave ones. After reviewing the state of the art of OSR, for which the diamond NV cen- ters constitute the benchmark, we undertake the study of fullerene-based species for OSR. An optically detected magnetic resonance (ODMR) setup was imple- mented in a commercial EPR spectrometer for this purpose. Each experimental chapter focuses on one of the molecular systems in question: a functionalised C60 fullerene with a phosphonate group (C60-phosphine), porphyrin-fullerene ar- chitectures (weakly, strongly and moderately coupled) and finally erbium-doped trimetallic nitride template (TNT) fullerenes (focusing on ErSc2N@C80). In the C60-phosphine system, coherent optically detected magnetic resonance (ODMR) in the triplet state has been achieved. Since a large variety of organic and organometallic molecules can be attached to it both via the fullerene cage and the phosponate group, this result makes it a very useful template to study OSR molecules chemically linked to a qubit. In the porphyrin based structures, an intermediate coupling case in the form of a trimer-fullerene host-guest complex is found to allow detection of both the porphyrin and fullerene triplet sates by CW ODMR, which makes organo-metallic complexes a possible coupling route for a qubit to an OSR component. In the TNT fullerene, crystal field mixing makes the Er3+ inaccessible by ODMR. However, optical photons cause a mechanical rearrangement of the en- dohedral cluster which in turns impacts on the observed EPR. In particular, the dynamics of this process have been studied for the first time and hint to- wards diffusion kinetics at low pump power. An orientational selectivity has been discovered by using a polarised pump, and the time dynamics indicate the rearrangement of the matrix via difusion on a free volume around the fullerenes. This shows that the endohedral Er3+ in ErSc2N@C80 can probe the environment outside the cage.
Supervisor: Briggs, G. A. D. ; Taylor, R. A. ; Ardavan, Arzhang ; Morton, J. J. L. Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Laser Spectroscopy ; Nanomaterials ; Magnetic Resonance ; Quantum Information ; Fullerene ; Erbium ; diffusion ; spectroscopy ; organometallic