Dynamical Self-Quenching of Spin Pumping into Double Quantum Dots

TL;DR

This paper reveals a self-quenching mechanism in nuclear spin polarization during spin pumping in quantum dots, explaining low polarization levels and suggesting the need for new protocols to overcome this limitation.

Contribution

The study uncovers a dynamical self-quenching process in nuclear spin pumping in quantum dots through numerical simulations, highlighting a universal screening mechanism that limits polarization.

Findings

Self-quenching causes rapid saturation of nuclear polarization.

Screening of nuclear and spin-orbit fields occurs during pumping.

The mechanism is robust under moderate noise.

Abstract

Nuclear spin polarization can be pumped into spin-blocked quantum dots by multiple Landau- Zener passages through singlet-triplet anticrossings. By numerical simulations of realistic systems including approximately $10^7$ nuclear spins during $10^5$ sweeps, we uncover a mechanism of dynamical self-quenching which results in a fast saturation of the nuclear polarization under stationary pumping. This is caused by screening of the field of the nuclear spins. In systems with moderate spin-orbit coupling, self-quenching also screens the spin-orbit interaction. The mechanism is generic and remains robust under a moderate noise. Our finding explains low polarization levels achieved experimentally and calls for developing new protocols that break the self-quenching limitations.