Charge transport and phase transitions in cobalt oxides studied by terahertz spectroscopy


Cobalt oxides comprise a wide group of materials in which important electron correlations lead to a large richness of interesting properties (e.g. large thermoelectric coefficient or superconductivity). The cobalt ions can frequently attain different electronic configurations, which is at the root of complex and often contradicting behaviors with varying temperature and material composition. Charge transport is one of the most important processes which reflect the internal state of these materials, and it is also of fundamental interest in potential applications. In cobaltites, we will study namely the mechanism of the metal-insulator transition. In layered cobaltates, we fill focus on the relation between charge transport and magnetic ordering. We will systematically study the conductivity in the terahertz spectral range, which permits a clear identification of charge transport mechanisms and charge confinement both in single crystals and in polycrystalline systems. Combination with common characterization methods will allow gaining a global picture of the behavior of the oxides.