Influence of Nuclear Quadrupole Moments on Electron Spin Coherence in   Semiconductor Quantum Dots
  We theoretically investigate the influence of the fluctuating Overhauser field on the spin of an electron confined to a quantum dot (QD). The fluctuations arise from nuclear angular momentum being exchanged between different nuclei via the nuclear magnetic dipole coupling. We focus on the role of the nuclear electric quadrupole moments (QPMs), which generally cause a reduction in internuclear spin transfer efficiency in the presence of electric field gradients. The effects on the electron spin coherence time are studied by modeling an electron spin echo experiment. We find that the QPMs cause an increase in the electron spin coherence time and that an inhomogeneous distribution of the quadrupolar shift, where different nuclei have different shifts in energy, causes an even larger increase in the electron coherence time than a homogeneous distribution. Furthermore, a partial polarization of the nuclear spin ensemble amplifies the effect of the inhomogeneous quadrupolar shifts, causing an additional increase in electron coherence time, and provides an alternative to the experimentally challenging suggestion of full dynamic nuclear spin polarization. 
Erik Welander, Evgeny Chekhovich, Alexander Tartakovskii, Guido   Burkard
cond-mat.mes-hall