| I review simple qualitative aspects of spin fluctuation pairing theory for the Fe-based superconductors which suggest how the superconducting state should evolve with doping or pressure. The 122 materials are used as a paradigm, and compared to "extreme over- or underdoped" systems, particularly the recently discovered alkaline iron selenide materials I discuss investigations of the consequences of the unusual features of these "extreme" Fe-based systems for the superconducting ground state symmetry and pair structure. |
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