Nanoscale Control of Quantum Materials

Research in UBC-TUM Collaboration

Prof. Douglas Bonn is focusing on the synthesis and physical properties of transition metal oxides, the high temperature superconducting cuprates in particular as a Hans Fischer Senior Fellow at TUM-IAS. The interest in the oxides lies in the strong interactions between electrons in these systems, which give rise to exotic physical properties and often also result in a high degree of tunability, by which small changes in chemical composition, pressure or magnetic field can profoundly influence the electronic ground state. This research is now entering a new era in which it is apparent that the strong correlations and tunabiltiy can lead to large effects at surfaces and interfaces. The UBC-TUM collaboration brings together Doug Bonn's work on the transition metal oxides with Prof. Johannes Barth's work on scanning tunnelling microscopy and spectroscopy. Together they can take the relatively complex surface of a transition metal oxide, explore the electronic properties of the surface with atomic resolution, and then seek to modify the properties through Barth's work on in situ deposition of atoms and molecules. For example, angle-resolved photoemission by Damascelli at UBC now indicates that the cleaved surface of YBa2Cu3O7 has a concentration of hole doping that differs dramatically from the bulk, evidence of a so-called 'polarization catastrophe'. Barth's STM allows an atomic resolution study of systematic modification of this surface through in situ deposition of sub-monolayers of ions and molecules, providing a new way of tuning an oxide's properties.

Dr. Willhelm Auwärter’s current research aims at the control of matter on solid surfaces. Using individual atoms and molecules as building blocks, supramolecular architectures and functional nanostructures are assembled on noble metal substrates. Combining scanning probe microscopy and spectroscopy with complementary non-local methods he addresses the geometric and electronic structure of such low-dimensional systems on an atomic level. During his Carl von Linde Junior Fellowship at TUM, he plans to extend his studies towards more complex substrates, specifically ultra-thin insulating films and half-metals, but also transition metal oxides. By combining the unusual electronic and magnetic properties of such complex surfaces with the inherent functionality of organic or biomolecular building blocks, he aims to achieve desired functionalities of the surface anchored nanostructures. From a different point of view, this approach complements Doug Bonn’s work providing procedures to modify and dope transition metal oxide surfaces.

TUM-IAS funded doctoral candidate:
Wolfgang Krenner (PhD in 2012)