Nesting between hole and electron pockets in Ba(Fe1-xCox)2As2 (x=0-0.3) observed with angle-resolved photoemission

We present a comprehensive angle-resolved photoemission study of the three-dimensional electronic structure of Ba(Fe1-xCox)(2)As-2. The wide range of dopings covered by this study, x=0 to x=0.3, allows to extract systematic features of the electronic structure. We show that there are three different hole pockets around the Gamma point: the two inner ones being nearly degenerate and rather two dimensional, the outer one presenting a strong three-dimensional character. The structure of the electron pockets is clarified by studying high doping contents, where they are enlarged. They are found to be essentially circular and two dimensional. From the size of the pockets, we deduce the number of holes and electrons present at the various dopings. We find that the net number of carriers is in good agreement with the bulk stoichiometry but that the number of each species (holes and electrons) is smaller than predicted by theory. Finally, we discuss the quality of nesting in the different regions of the phase diagram. The presence of the third hole pocket significantly weakens the nesting at x=0, so that it may not be a crucial ingredient in the formation of the spin-density wave. On the other hand, superconductivity seems to be favored by the coexistence of two-dimensional hole and electron pockets of similar sizes.