HIGH-RESOLUTION ANGLE-RESOLVED PHOTOEMISSION STUDY OF BaCo1-xNixS2

We have performed angle-resolved photoemission spectroscopy on a layered Mott system BaCo1-xNixS2 across the phase transition from the antiferromagnetic insulator (x = 0.18) to anomalous metal (x = 0.28). In the anomalous metallic phase, we found a large Fermi surface centered at the M(A) point with a dominant Co (Ni) 3d3z2-r2 character. Hubbard bands in the insulating phase have a remnant of Fermi surface in the metallic phase and gradually evolve into metallic dispersive bands upon carrier doping. We conclude that the electronic structure of BaCo1 - xNixS2 is basically different from that of the high-Tc cuprates although the transport and magnetic properties share some common features between the two layered compounds.