Univ. Augsburg
Interfaces in complex transition metal oxide heterostructures can play
an important role for their physical properties. This is especially
important for heterostructures
which contain nm-thick films deposited on structurally compatible
substrate layers. The lattice mismatch and the charge polarity due to
structural discontinuities at a film-substrate
interface are the driving forces of interfacial reconstruction which
changes dramatically the interface electronic state and possibly the
physical behavior of the entire film.
Frequently used as a model system for oxide interfaces, the interface
between the charge transfer insulators LaAlO3 and TiO3-terminated SrTiO3
forms an especially peculiar ultra-thin metallic state with fascinating
properties. At low temperatures, for example, this state forms a
tunable, two-dimensional superconductor. However, little is known about
the microscopic nature of this electronic phase. We have therefore
investigated the electronic structure of the interfaces by scanning
tunneling spectroscopy (STS). The density of states (DOS) determined by
STS is in excellent agreement with local density approximation
calculations, if sufficiently strong on-site repulsion is taken into
account.