Optical NMR in Semiconductors

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Science  30 Mar 2001:
Vol. 291, Issue 5513, pp. 2519
DOI: 10.1126/science.291.5513.2519a

The relatively long lifetimes of nuclear spins compared to electron spins and their inherent resilience to decoherence offer an alternative route for exploring device architectures based on spin manipulation. In this regard, the hyperfine interaction between optically excited precessing electrons and the nuclei has been proposed as a technique for nuclear spin manipulation. However, an earlier paper described resonances that did not correspond clearly to any nuclear moments present in the sample.

Using a new system in which the electrons are restricted to a two-dimensional plane, Salis et al. establish that connection unambiguously for transitions of 69Ga, 71Ga, and 75As. A circularly polarized pump pulse excites the electrons, which then precess around an out-of-plane magnetic field. The nuclei are highly polarized, and depending on the extent of the asymmetry of magnetic field, the nuclear spin can be polarized controllably along or against the direction of the magnetic field. The signals seen in the previous study turn out to be normally forbidden Δm = 2 transitions at half the conventional resonance frequency. — ISO

Phys. Rev. Lett.86, 2677 (2001).

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