Polar surface engineering in ultra-thin MgO(111)/Ag(111) -- possibility   of metal-insulator transition and magnetism
  A recent report [Kiguchi {\it et al.}, Phys. Rev. B {\bf 68}, 115402 (2003)] that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes metallic to reduce the electric dipole moment raises a question of what will happen when we have fewer MgO layers. Here we have revealed, first experimentally with electron energy-loss spectroscopy, that MgO(111) remains metallic even when one-layer thick, and theoretically with the density functional theory that the metallization should depend on the nature of the substrate. We further show, with a spin-density functional calculation, that a ferromagnetic instability may be expected for thicker films. 
Ryotaro Arita, Yoshiaki Tanida, Shiro Entani, Manabu Kiguchi, Koichiro   Saiki, and Hideo Aoki