Evidence for a preformed Cooper pair model in the pseudogap spectra of a Ca10(Pt4As8)(Fe2As2)5 single crystal with a nodal superconducting gap

摘要

For high-Tc superconductors, clarifying the role and origin of the pseudogap is essential forunderstanding the pairing mechanism. Among the various models describing the pseudogap, thepreformed Cooper pair model is a potential candidate. Therefore, we present experimental evidencefor the preformed Cooper pair model by studying the pseudogap spectrum observed in the opticalconductivity of a Ca10(Pt4As8)(Fe2As2)5 (Tc=?34.6?K) single crystal.We observed a clear pseudogapstructure in the optical conductivity and observed its temperature dependence. In the superconducting(SC) state, one SC gap with a gap size of Δ=?26?cm?1, a scattering rate of 1/τ=?360?cm?1 and a lowfrequencyextra Drude component were observed. Spectral weight analysis revealed that the SCgap and pseudogap are formed from the same Drude band. This means that the pseudogap is a gapstructure observed as a result of a continuous temperature evolution of the SC gap observed below Tc.This provides clear experimental evidence for the preformed Cooper pair model.