Evidence of a pseudogap for superconducting iron-pnictide Ba0.6+delta K0.4-delta Fe2As2 single crystals from optical conductivity measurements

Abstract

We report the observation of pseudogap (PG) behavior in optical conductivity in an underdoped Ba 0.6+δK 0.4-δFe 2As 2 (T c onsetc≈ 36 K) single crystal far above T c, up to 100K (≈ 3T c). Wide separation of the energy scales of the magnetic and superconducting (SC) correlations in the Ba 0.6+δK 0.4-δFe 2As 2 sample enabled us to establish that the PG structures observed in optical conductivity in the range of 50-150 cm -1 are uniquely driven by the SC correlation, and the magnetic correlation coexists in the far separated range of about 700 cm -1. Theoretical calculations, based on the preformed Cooper pair model, provided an excellent description of the temperature evolution of the SC correlation in optical conductivity data from below to above T c. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.