Optical NMR from single quantum dots

Abstract

Nuclear magnetic resonance (NMR) from constituent Ga and As nuclei was optically detected on excitonic recombination in single GaAs quantum dots formed by interface fluctuations in GaAs/Al 0.3Ga 0.7As quantum wells. Orientation of the nuclear spin system by optical pumping causes an Overhauser shift of the excitonic energy levels proportional to the degree of nuclear orientation. NMR was subsequently detected by monitoring changes in the combined Overhauser plus Zeeman splitting of excitons localized in single quantum dots as the RF frequency was swept through a nuclear resonance. The NMR signals originate from ∼10 5 nuclei in the quantum dot—with dimensions of approximately 4 nm×10 nm×100 nm—illustrating the extreme sensitivity and spatial resolution of the technique. NMR from such small structures provides a chemically specific probe of the local environment on the nanometer scale.