Condensed-Matter Physics & Materials Science Seminar

Carefully controlled interfaces between two different materials can give rise to novel physical phenomena and functionalities not exhibited by either of the constituent materials alone, like the quantum Hall effect in semiconductor multilayers and the “giant magnetoresistance” effect in superlattices of simple metals. Interfaces between transitionmetal-oxides exhibiting strong electron correlation effects can exhibit properties not observed at semiconductor or ordinary metal interfaces, such as emergent superconductivity. This can open a path towards a new generation of electronic devices. Especially interfaces with transition metal oxides with partially occupied d-orbitals exhibit a large variety of electronic phases with often radically different physical properties, even in bulk form. The phase behavior of these systems is rooted in the delicate sensitivity of the charge transfer and magnetic interaction between metal ions to the d-orbital occupation. In this talk experimental results of physical properties of superconducting YBCO and ferromagnetic LCMO superlattices will briefly be reviewed as a case study for technological possibilities for interface engineering. Using this knowledge we focus on heterostructures based on nickelates with preovskite structure with the intention to mimick the cuprate case and potentially generate new quantum states at the interface. The heterostructures are synthesized with atomic precision using pulsed-laser deposition, and investigated with spectroscopic methods such as X-ray linear and circular dichrosim, resonant X-ray reflectometry, and spectral ellipsometry, as well as aberration-corrected highresolution electron diffraction. The goal of this investigation is a detailed understanding of the relationship between the atomic structure and the electronic properties at the interfaces, with particular focus on the valence states, orbital occupation, and charge transport.