Abstract
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. Here we 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, we observe that the size of the spin–orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin–orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin–orbit coupling in central-spin systems.
Highlights
The central-spin problem is a widely studied model of quantum decoherence
The relationship between the spin–orbit and hyperfine interactions[17,18,19,20] has been overlooked in previous experimental studies of Dynamic nuclear polarization (DNP) in quantum dots, several works have shown that the spin–orbit and hyperfine interactions contribute to spin relaxation[21,22,23] under different conditions
We show that spin–orbit coupling competes with the hyperfine interaction and quenches DNP in a GaAs double quantum dot[14,25], even though the spin–orbit length is much larger than the interdot spacing
Summary
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. The relationship between the spin–orbit and hyperfine interactions[17,18,19,20] has been overlooked in previous experimental studies of DNP in quantum dots, several works have shown that the spin–orbit and hyperfine interactions contribute to spin relaxation[21,22,23] under different conditions. It has been theoretically predicted, not observed experimentally, that the spin–orbit interaction should limit DNP by providing a route for electron spin flips without corresponding nuclear spin flops[18,20,24]. In addition to improving basic understanding of DNP in semiconductors, these results will enable enhanced coherence times in semiconductor spin qubits by elucidating the experimental conditions under which DNP is most efficient[26]
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