Physics of Transition Metal Oxides and Related Materials

Florida State University, Tallahassee FL

Investigators

Abstract

This award supports theoretical research with a computational emphasis, on colossal magneto resistance materials, high temperature superconductors, and other correlated transition metal materials. The research has several aims: (1) A complex mixed-phase paramagnetic-insulating state arises from the competition between metallic and insulating phases; the idea that this colossal magneto resistance also arises from this competition will be investigated. (2) Charge ordering in models for manganites will be analyzed with emphasis on the unexplored region of intermediate hole densities where correlated polaron physics has been revealed in recent experiments. The possibility of pseudogap formation in this region will be explored. (3) Physics common to the cuprates, manganates and other transition metal oxides in the inhomogeneous states will be examined. Stripes and superconductivity will be explored in the copper oxides using advanced methods to search for pairing and models that reproduce known experimental results reasonably well. These large-scale structures appear to be part of the common physics in cuprates and manganates. (4) Models for dilute magnetic semiconductors, Mn-doped GaAs semiconductors, will be studied. It is anticipated that the electronic properties of these materials will have features in common with those of the mixed-phases in the manganese oxides. %%% This award supports theoretical research with a computational emphasis, on colossal magneto resistance materials, high temperature superconductors, ruthenates and doped magnetic semiconductors. Colossal magneto resistance materials show an enormous change in resistivity with the application of modest magnetic fields and like the doped magnetic semiconductors, may be important in the emerging field of spintronics. These transition metal materials with strong electronic correlations can exhibit exotic electronic states, including large-scale structure or striped phases and the appearance of a pseudogap in the electronic excitation spectrum. In one thrust of the research, the PIs will use state of the art Monte-Carlo methods to investigate whether these phenomena share a common physical basis. The PIs will also investigate the common features of manganates and materials useful for spintronics applications, and elucidate the physical origin of the complex phase diagram of Ca2-x Srx RuO4 which includes paramagnetic, ferromagnetic, and antiferromagnetic phases. ***