Opening of the superconducting gap in the hole pockets of Ba(Fe1-xCox)(2)As-2 as seen via angle-resolved photoelectron spectroscopy

We present an angle-resolved photoelectron spectroscopy study of the changes in the electronic structure of electron-doped Ba(Fe1-xCox)(2)As-2 across the superconducting phase transition. By changing the polarization of the incoming light, we were able to observe the opening of the gap for the inner hole pocket alpha and to compare its behavior with the outer holelike band beta. Measurements along high-symmetry directions show that the behavior of beta is consistent with an isotropic gap opening, while slight anisotropies are detected for the inner band alpha. The implications of these results for the s +/- symmetry of the superconducting order parameter are discussed, in relation to the nature of the different iron orbitals contributing to the electronic structure of this multiband system.