Optical Nmr From Single Quantum Dots

Abstract

AbstractWe have observed nuclear magnetic resonance (NMR) signatures from constituent Ga and As nuclei in single GaAs quantum dots formed by interface fluctuations in GaAs/AlGaAs quantum wells. Orientation of the nuclear spin system by optical pumping causes an Overhauser shift in the excitonic energy levels proportional to the degree of nuclear orientation. NMR was detected by monitoring changes in the combined Overhauser plus Zeeman splitting of an exciton localized in a single quantum dot as the RF frequency was swept through a nuclear resonance. The NMR signals originate from ∼105 nuclei in the quantum dot — (20 nm)3 volume - representing an increase in sensitivity of five orders of magnitude over previous optical NMR measurements and thirteen orders of magnitude over conventional NMR. The data were fit to Lorentzian lineshapes, giving 75As linewidths on the order of 20 kHz.