Author ORCID Identifier
Date of Award
2-2024
Document Type
Thesis (Ph.D.)
Department or Program
Physics and Astronomy
First Advisor
Chandrasekhar Ramanathan
Abstract
Electron spins of point defects in diamond and silicon can exhibit long coherence times, making them attractive platforms for the physical implementation of qubits for quantum sensing and quantum computing. To realize these technologies, it is essential to understand the mechanisms that limit their coherence. Decoherence of these systems is well described by the central spin model, wherein the central electron spin weakly interacts with numerous electron and nuclear spins in its environment. The dynamics of the resultant dephasing can be probed with pulse electron paramagnetic resonance (pEPR) experiments.
Using a 2.5 GHz pEPR spectrometer built in-house, we performed multi-pulse dynamical decoupling (DD) noise spectroscopy experiments on ensembles of substitutional nitrogen (P1) and nitrogen-vacancy (NV) centers in diamond, which reveal a 1/$\omega$ power spectrum of the spin bath interactions. This behavior is indicative of a heterogeneous distribution of nitrogen impurities with varying noise correlation times, reinforcing the emerging picture that nitrogen defects can cluster in diamond. Novel DD analysis methods are introduced which utilize harmonic resonances to extend the frequency range for detecting peaks in the power spectrum. These methods are used to quantify the power spectral contribution of the precession of the 1.1\% abundant carbon-13 nuclei and could be used in a variety of ac magnetic field sensing protocols.
Experiments on phosphorus-doped silicon, performed on the 240 GHz EPR spectrometer at the National High Magnetic Field Laboratory, have revealed that the donor-bound electron coherence times are nominally shorter than theory predicts by a factor of 2, but when the sample is illuminated with above bandgap light, the coherence times are restored. These results are doubly surprising as they suggest that (i) silicon hyperfine interactions are modified at high magnetic fields; and (ii) optical excitation can extend coherence times, counter to what has been previously observed. While the microscopic details of this are unclear, these findings could inform models of spin dynamics in silicon.
Recommended Citation
Williams, Ethan Que, "PROBING CENTRAL SPIN DECOHERENCE DYNAMICS OF ELECTRONIC POINT DEFECTS IN DIAMOND AND SILICON" (2024). Dartmouth College Ph.D Dissertations. 222.
https://digitalcommons.dartmouth.edu/dissertations/222