Two-Dimensional Spin-Polarized Electron Gas at the Perovskite Manganite Interface : SrMnO$_3$/LaMnO$_3$

Electronic structure calculations for the perovskite manganite heterostructure (SrMnO$_3$)$_{n}$/(LaMnO$_3$)$_{1}$/(SrMnO$_3$)$_{n}$ reveal the presence of a novel spin-polarized electron gas at the interface, generated from the stripped-off La (5d$^1$) electrons, which become confined in the electrostatic V-shaped potential well of the positively charged (LaO) sheet, occupying the Mn(e$_g$) states near the interface. The presence of these electrons turns the interaction between the interfacial Mn atoms to be ferromagnetic via the Anderson-Hasegawa double exchange, overcoming the original antiferromagnetic superexchange present in the SrMnO$_3$ bulk. The FM Mn atoms at the interface in turn make the electron gas spin-polarized, as confirmed by the total energy calculations, and the type G AFM of the bulk is resumed a few layers into the bulk.