  Perovskite oxide interfaces have attracted tremendous research interest for
their fundamental physics and promising all-oxide electronics applications.
Here, based on first-principles calculations, we propose a novel surface La
interstitial promoted interface insulator-metal transition in LaAlO3/SrTiO3
(110). Compared with surface oxygen vacancies, which play a determining role on
the insulator-metal transition of LaAlO3/SrTiO3 (001) interfaces, we find that
surface La interstitials can be more experimentally realistic and accessible
for manipulation and more stable in ambient atmospheric environment.
Interestingly, these surface La interstitials also induce significant
spin-splitting states with Ti dyz/dxz character at conducting LaAlO3/SrTiO3
(110) interface. On the other hand, for insulating LaAlO3/SrTiO3 (110) (<4 unit
cells LaAlO3 thickness), a distortion between La (Al) and O atoms is found at
the LaAlO3 side, partially compensating the polarization divergence. Our
results reveal the origin of metal-insulator transition in LaAlO3/SrTiO3 (110)
heterostructures, and also shed light on the manipulation of the superior
properties of LaAlO3/SrTiO3 (110) for new possibilities of electronic and
magnetic applications.
