Figure 2

Side view of the relaxed structure, electron density distribution, integrated over occupied Ti 3d bands between E_F-1.5 eV and E_F and band structure of (LAO)_M/(STO)_N (001) SL at a_LAO, N = 2–4.

Majority and minority bands are plotted in blue and orange, respectively. Character plotting highlights the occupied d band at the Ti³⁺ sites. (a) For N = 2 a Dimer Mott insulator is obtained for the strongly compressed c parameter with alternating d_xz, d_yz orbital occupation at the Ti^3.5+ sites; (b) for the optimized c a charge ordered state with d_xz and d_yz orbital occupation at the Ti³⁺ sites at each interface layer emerges; ΔE is the energy difference (in eV per Ti site) between the cases shown in (b) and (a); (c) N = 3 is similar to (b) with Ti⁴⁺ in the central layer; (d) an insulator to metal transition takes place for N = 4: with a d_xy orbital polarization at the Ti interface sites and d_xz + d_yz orbital occupation in the inner STO layers.