Correlated Electron Systems

In sodium cobaltate (Na_xCoO₂) the electrons in the CoO₂ layers are strongly correlated and give rise to a very large thermoelectric effect. The sodium ions in between the CoO₂ layers are mobile at elevated temperatures and arrange in various ordering patterns. Our research concentrates on the dependence of magnetic ground states and the electronic transport properties on changes in the sodium ordering. Using a defined cooling protocol we are able to induce different sodium orderings and investigate the resulting electronic ground states employing various techniques, such as electronic transport, specific heat or magnetisation measurements.