title: Charge ordering, commensurability, and metallicity in the phase diagram of the layered NaxCoO2.
abstract: The phase diagram of nonhydrated NaxCoO2 has been determined by changing the Na content x using a series of chemical reactions. As x increases from 0.3, the ground state goes from a paramagnetic metal to a charge-ordered insulator (at x=1/2), then to a "Curie-Weiss metal" (around 0.70), and finally to a weak-moment magnetically ordered state (x>0.75). The unusual properties of the state at 1/2 (including particle-hole symmetry at low T and enhanced thermal conductivity) are described. The strong coupling between the Na ions and the holes is emphasized.
authors.affiliation: Department of Chemistry, Princeton University, New Jersey 08544, USA.
authors.forename: Maw Lin
authors.initials: ML
authors.lastname: Foo
authors.forename: Yayu
authors.initials: Y
authors.lastname: Wang
authors.forename: Satoshi
authors.initials: S
authors.lastname: Watauchi
authors.forename: H W
authors.initials: HW
authors.lastname: Zandbergen
authors.forename: Tao
authors.initials: T
authors.lastname: He
authors.forename: R J
authors.initials: RJ
authors.lastname: Cava
authors.forename: N P
authors.initials: NP
authors.lastname: Ong