  We investigated the effect of the tensile strain on the spin splitting at the
n-type interface in LaAlO$_3$/SrTiO$_3$ in terms of the spin-orbit coupling
coefficient $\alpha$ and spin texture in the momentum space using
first-principles calculations. We found that the $\alpha$ could be controlled
by the tensile strain and be enhanced up to 5 times for the tensile strain of
7%, and the effect of the tensile strain leads to a persistent spin helix,
which has a long spin lifetime. These results support that the strain effect on
LaAlO$_3$/SrTiO$_3$ is important for various applications such as spinFET and
spin-to-charge conversion.
