Orbital physics and spin-orbit interaction
The interplay between charge, orbital, and magnetic degrees of freedom results in a wide variety of physical phenomena and properties in particular in compounds with strong electronic correlations. High-temperature superconductivity, colossal magnetoresistance, and multiferroic magnetoelectrics are probably the most famous examples that all bear a strong potential for applications. Research in Cologne has clarified the microscopic nature of such complex order in many materials such as manganites, nickelates, vanadates, and cobaltates using a combination of various efforts ranging from theory, material synthesis, macroscopic and transport properties, to a wide range of spectroscopic methods. Spin orbit interactions drive a broad range of phenomena including topological insulators, multiferroics, and skyrmions in chiral magnets and may lead to spin-orbit driven Mott states.