A global quantitative picture of the phonon-induced two-electron spin
relaxation in GaAs double quantum dots is presented using highly accurate
numerical calculations. Wide regimes of interdot coupling, magnetic field
magnitude and orientation, and detuning are explored in the presence of a
nuclear bath. Most important, the unusually strong magnetic anisotropy of the
singlet-triplet relaxation can be controlled by detuning switching the
principal anisotropy axes: a protected state becomes unprotected upon detuning,
and vice versa. It is also established that nuclear spins can dominate spin
relaxation for unpolarized triplets even at high magnetic fields, contrary to
common belief. These findings are central to designing quantum dots geometries
for spin-based quantum information processing with minimal environmental
impact.Comment: 8 pages, 8 figure
