From the SrTiO3 Surface to the LAlO3/SrTiO3 Interface: How thickness is critical

摘要: Novel properties arising at interfaces between transition metal oxides, particularly the conductivity interface of LaAlO3 (LAO) and SrTiO3 (STO) band insulators, have generated new paradigms, challenges, opportunities in condensed matter physics. Conventional transport measurements established that intrinsic appears LAO/STO when LAO film matches or exceeds a critical thickness 4 unit cells (uc). Recently, number experiments raise important questions about role film, influence photons, effective differences vacuum/STO LAO/STO, both above below standard thickness. Here, using angle-resolved photoemission spectroscopy (ARPES) on situ prepared samples, as well resonant inelastic x-ray scattering (RIXS), we study how metallic STO surface state evolves during growth crystalline film. In all character conduction bands, their carrier densities, Ti3+ crystal fields, responses to photon irradiation bear strong similarities. However, exhibit instability toward in-plane folding Fermi 4-uc threshold. This ordering distinguishes these heterostructures from bare sub-critical-thickness coincides with onset unique such magnetism built-in conductivity.