Dynamic Nuclear Polarization in Double Quantum Dots

TL;DR

This paper theoretically explores how nuclear spins in GaAs double quantum dots can be dynamically polarized, revealing three regimes of long-term behavior including field differences, saturation, and elimination of differences.

Contribution

It identifies and characterizes three distinct regimes of nuclear spin dynamics in double quantum dots, including the formation of dark states and the conditions for eliminating Overhauser field differences.

Findings

Build-up of Overhauser field differences in unequal dots.

Saturation of nuclear polarization via dark states.

Elimination of difference fields is not always a stable steady state.

Abstract

We theoretically investigate the controlled dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. Three regimes of long-term dynamics are identified, including the build up of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with formation of so-called "dark states," and the elimination of the difference field. We show that in the case of unequal dots, build up of difference fields generally accompanies the nuclear polarization process, whereas for nearly identical dots, build up of difference fields competes with polarization saturation in dark states. The elimination of the difference field does not, in general, correspond to a stable steady state of the polarization process.