Abstract
We used angle-resolved photoemission spectroscopy and thermoelectric power to study the poorly explored, highly overdoped side of the phase diagram of Ba(FeCo)As high-temperature superconductor. Our data demonstrate that several Lifshitz transitions—topological changes of the Fermi surface—occur for large . The central hole barrel changes to ellipsoids that are centered at at and subsequently disappear around ; changes in thermoelectric power occur at similar values. decreases and goes to zero around —between the two Lifshitz transitions. Beyond the central pocket becomes electron-like and superconductivity does not exist. Our observations reveal the importance of the underlying Fermiology in electron-doped iron arsenides. We speculate that a likely necessary condition for superconductivity in these materials is the presence of the central hole pockets rather than nesting between central and corner pockets.
- Received 12 June 2011
DOI:https://doi.org/10.1103/PhysRevB.84.020509
©2011 American Physical Society