Dynamic spin polarization
Researchers from the Institute for Molecular Engineering (IME) have developed a model that provides a detailed description of the dynamic nuclear spin polarization process of point defects with a high ground-state electronic spin and adjacent nuclear spins.
The team of IME researchers were from the Awschalom Research Group led by University of Chicago Professor and Argonne Joint Appointment David Awschalom. The findings have been published in Physical Review B.
Point defects in solids are promising implementations of quantum bits for quantum computing. In particular, the negatively charged nitrogen-vacancy defect (NV center) in diamond has become a leading system in solid-state quantum-information processing because of its unique magnetooptical properties, including long spin coherence times and the ease of optical initialization and readout of its spin state, even nondestructively. Since it has a high-spin electronic structure similar to the NV center in diamond, the divacancy in silicon carbide (SiC) has also been proposed to serve as a solid-state quantum bit.
Dynamic nuclear spin polarization (DNP) mediated by paramagnetic point defects in semiconductors is a key resource for both initializing nuclear quantum memories and producing nuclear hyperpolarization. DNP is therefore an important process in the field of quantum-information processing, sensitivity-enhanced nuclear magnetic resonance, and nuclear-spin-based spintronics. DNP based on optical pumping of point defects has been demonstrated by using the electron spin of nitrogen-vacancy (NV) center in diamond, and more recently, by using divacancy and related defect spins in hexagonal silicon carbide (SiC).
Here, we describe a general model for these optical DNP processes that allows the effects of many microscopic processes to be integrated. Applying this theory, we gain a deeper insight into dynamic nuclear spin polarization and the physics of diamond and SiC defects. Our results are in good agreement with experimental observations and provide a detailed and unified understanding. In particular, our findings show that the defect electron spin coherence times and excited state lifetimes are crucial factors in the entire DNP process.
Viktor Ivády, Krisztián Szász, Abram L. Falk, Paul V. Klimov, David J. Christle, Erik Janzén, Igor A. Abrikosov, David D. Awschalom and Adam Gali, “Theoretical Model of Dynamic Spin Polarization of Nuclei Coupled to Paramagnetic Point Defects in Diamond and Silicon Carbide,” Physical Review B, 92, 115206, DOI: 10.1103/PhysRevB.92.115206. Published Online September 18, 2015.