title: Electron-hole asymmetry in GdBaCo2O(5+x): evidence for spin blockade of electron transport in a correlated electron system.
abstract: In RBaCo2O(5+x) compounds (R is rare earth), the variability of the oxygen content allows precise doping of CoO2 planes with both types of charge carriers. We study transport properties of doped GdBaCo2O(5+x) single crystals and find a remarkable asymmetry in the behavior of holes and electrons doped into a parent insulator GdBaCo2O(5.5). The doping dependencies of resistivity, Hall response, and thermoelectric power reveal that the doped holes greatly improve the conductivity, while the electron-doped samples always remain poorly conducting. This doping asymmetry provides strong evidence for a spin blockade of the electron transport in RBaCo2O(5+x).
authors.affiliation: Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511, Japan.
authors.forename: A A
authors.initials: AA
authors.lastname: Taskin
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ando