Enhancement of T c by disorder in underdoped iron pnictide superconductors

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Abstract

We analyze how disorder affects the transition temperature T c of the s +- superconducting state in the iron pnictides. The conventional wisdom is that T c should rapidly decrease with increasing inter-band nonmagnetic impurity scattering, but we show that this behavior holds only in the overdoped region of the phase diagram. In the underdoped regime, where superconductivity emerges from a pre-existing magnetic state, disorder gives rise to two competing effects: breaking of the Cooper pairs, which tends to reduce T c, and suppression of the itinerant magnetic order, which tends to bring T c up. We show that for a wide range of parameters the second effect wins; i.e., in the coexistence state T c can increase with disorder. Our results provide an explanation for several recent experimental findings and lend additional support to s +- pairing in the iron pnictides.

Original languageEnglish (US)
Article number140512
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number14
DOIs
StatePublished - Apr 23 2012

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