Orbital configuration in CaTiO_3 films on NdGaO_3

摘要

Despite its use as a constituent layer for realization of a polar metal and interfacial conductivity, the microscopic study of electronic structure of CaTiO_3 is still very limited. Here, we epitaxially stabilized CaTiO_3 films on NdGaO_3 (110) substrates in a layer-by-layer way by pulsed laser deposition. The structural and electronic properties of the films were characterized by reflection-high-energy-electron-diffraction, X-ray diffraction, and element-specific resonant X-ray absorption spectroscopy. To reveal the orbital polarization and the crystal field splitting of the titanium 3d state, X-ray linear dichroism was carried out on CaTiO_3 films, demonstrating the orbital configuration of d_(xz)/d_(yz)＜ d_(xy) ＜ d_(3z~2-r~2) ＜ d_(x~2-y~2). To further explore the origin of this configuration, we performed the first-principles density function theory calculations, which linked the orbital occupation to the on-site energy of Ti 3d orbitals. These findings can be important for understanding and designing exotic quantum states in heterostructures based on CaTiO_3.