Studying Magnetic-Polaron Cooper-Pair-breaking Effects in Bi2Sr2CaCu2O8+δ by Femtosecond Photoexcitation

The relation between magnetism and superconductivity, whether magnetism is beneficial to superconductivity or they permit co-existence and competition, has been a long debate in the high-temperature superconducting field. Here, to explore this odd issue, we study the relaxation dynamics of photoinduced magnetic-polaron and superconductivity quasiparticles by an ultrafast time-resolved optical reflectivity technology in Bi2Sr2CaCu2O8+δ . When the pump fluence F is less than 7 mW, time-resolved reflection spectrum ΔR(t)/R 0 is dominated by the superconducting component. It is noteworthy that a large of photoinduced magnetic-polaron component can cause the inhibition of the superconducting component when the variable pump fluence F is more than the value 7 mW. It can be attributed to the strong photoinduced magnetic-polaron Cooper-pair-breaking mechanism. Further studies have shown that the photoinduced magnetic-polaron Cooper-pair-breaking mechanism is similar to the pair-breaking effect caused by the magnetic impurity Fe in the Bi2Sr2CaCu2O8+δ superconductor, although the forms of their action are different.