Electron-lattice and strain effects in manganite heterostructures: the case of a single interface

A correlated inhomogeneous mean-field approach is proposed to study a tight-binding model of the manganite heterostructures (LaMnO3)2n/(SrMnO3)n with average hole doping x = 1/3. Phase diagrams and spectral and optical properties of large heterostructures (up to 48 sites along the growth direction) with a single interface are discussed, and the effects of electron-lattice antiadiabatic fluctuations and strain are analyzed. The formation of a metallic ferromagnetic interface is quite robust upon varying the strength of electron-lattice coupling and strain, though the size of the interface region is strongly dependent on these interactions. The density of states never vanishes at the chemical potential due to the formation of the interface, but it shows a rapid suppression with increasing the electron-lattice coupling. The in-plane and out-of-plane optical conductivities show sharp differences since the in-plane response has metallic features, while the out-of-plane one is characterized by a transfer of spectral weight to high frequency. The in-plane response mainly comes from the region between the two insulating blocks, so that it provides a clear signature of the formation of the metallic ferromagnetic interface. Results are discussed in connection with available experimental data.