Spin and charge in electrochemically doped oxides

点击翻译按钮获取中文摘要

The physics of transition metal oxides is one of the most fascinating and very important topics in contemporary condensed matter research. The physical properties of these systems are controlled by the combination and competition of several degrees of freedom, the charge, the spin and the orbital state of the electrons. This interplay gives rise to a rich variety of ground states. Technologically important are, e.g., the high temperature superconducting cuprates and the manganites with colossal magnetoresistance. One important parameter responsible for the physical properties in these Systems is the density of charge carriers which determines the oxidization state of the transition metal. In most experimental studies reported to date the charge carrier density is adjusted either by a partial substitution of the cations via a solid state reaction or by a modification of the oxygen content via a thermal treatment under a controlled oxygen athmosphere. Therefore the physics in these systems is considerably influenced by steric effects and disorder. The central objective of this research program is the study of transition metal oxides in which the charge carrier density is adjusted and controlled via electrochemistry. This method is based on the extraction and insertion of light alcaline metal ions in the crystal lattice which directly changes the valence of the transition metal. It allows the preparation of extraordinary oxidization states with new physical properties. Lithium based transition metal oxides are also used as state-of-the-art rechargable power sources. Therefore a deep understanding of the structural and electronic properties of these Systems is also of high technological interest.