A Laser‐ARPES View of the 2D Electron Systems at LaAlO3/SrTiO3 and Al/SrTiO3 Interfaces

The electronic structure of the two‐dimensional electron system (2DES) found at the Al/SrTiO3 (Al/STO) and LaAlO3/SrTiO3 (LAO/STO) interfaces is measured by means of laser angle resolved photoemission spectroscopy, taking advantage of the large photoelectron escape depth at low photon energy to probe these buried interfaces. The possibility of tuning the electronic density in Al/STO by varying the Al layer thickness is demonstrated, and it is shown that the electronic structure evolution is well described by self‐consistent tight binding supercell calculations, but differs qualitatively from a rigid band shift model. It is shown that both 2DES are strongly coupled to longitudinal optical phonons, in agreement with previous reports of a polaronic ground state in similar STO based 2DESs. Tuning the electronic density in Al/STO to match that of LAO/STO and comparing both systems, it is estimated that the intrinsic LAO/STO 2DES has a bare band width of ≈60 meV and a carrier density of ≈6 × 1013 cm−2. The electronic structure of the 2D electron systems found at the Al/SrTiO3 (STO) and LaAlO3 (LAO)/SrTiO3 interfaces is measured by laser angle resolved photoemission spectroscopy. Comparison to self‐consistent tight binding supercell calculations demonstrates that the evolution of the Al/SrTiO3 band structure with density deviates from a rigid band shift model. The electronic density in Al/STO is tuned to match that of LAO/STO allowing a comparison of these two systems.