Quenching of Dynamic Nuclear Polarization by Spin–Orbit Coupling in GaAs Quantum Dots

July 21, 2015
Figure 3: Correlations and power spectrum of PLZ(t)

Fig. 3: Correlations and power spectrum of PLZ(t). [Reprinted by permission from Macmillan Publishers Ltd: Nature Communications ©2015*]

The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood.

In an article* in Nature Communications, professors Amir Yacoby and Bertrand Halperin, postdocs John Nichol and Arijeet Pal, grad students Shannon Harvey and Michael Shulman, research scholar Emmanuel Rashba, and Vladimir Umansky from Weizmann Institute of Science, Israel, show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, the authors observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. They find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Their results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.

*See J.M. Nichol, et al., "Quenching of dynamic nuclear polarization by spin–orbit coupling in GaAs quantum dots," Nature Communications 6 (17 July 2015) doi:10.1038/ncomms8682.