



01759nas a2200169   4500008004100000245008100041210006900122260001400191490000700205520124300212100002101455700001801476700001901494700002101513700001801534856003701552       2013                        eng d00aPreparation of Non-equilibrium Nuclear Spin States in Double Quantum  Dots
0 aPreparation of Nonequilibrium Nuclear Spin States in Double Quan  c2013/7/150 v883 a  We theoretically study the dynamic polarization of lattice nuclear spins in
GaAs double quantum dots containing two electrons. In our prior work [Phys.
Rev. Lett. 104, 226807 (2010)] we identified three regimes of long-term
dynamics, 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. In particular, when the dots are different sizes we found
that the Overhauser field becomes larger in the smaller dot. Here we present a
detailed theoretical analysis of these problems including a model of the
polarization dynamics and the development of a new numerical method to
efficiently simulate semiclassical central-spin problems. When nuclear spin
noise is included, the results agree with our prior work indicating that large
difference fields and dark states are stable configurations, while the
elimination of the difference field is unstable; however, in the absence of
noise we find all three steady states are achieved depending on parameters.
These results are in good agreement with dynamic nuclear polarization
experiments in double quantum dots.
1 aGullans, Michael1 aKrich, J., J.1 aTaylor, J., M.1 aHalperin, B., I.1 aLukin, M., D.  uhttp://arxiv.org/abs/1212.6953v301401nas a2200217   4500008004100000245005600041210005600097260001300153490000800166520081300174100002100987700001801008700001901026700001401045700002101059700001901080700001401099700001501113700001801128856003701146       2010                        eng d00aDynamic Nuclear Polarization in Double Quantum Dots0 aDynamic Nuclear Polarization in Double Quantum Dots  c2010/6/40 v1043 aWe 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.
1 aGullans, Michael1 aKrich, J., J.1 aTaylor, J., M.1 aBluhm, H.1 aHalperin, B., I.1 aMarcus, C., M.1 aStopa, M.1 aYacoby, A.1 aLukin, M., D.  uhttp://arxiv.org/abs/1003.4508v2