Ultrafast Jahn-Teller polaron dynamics in a bi-layered manganite single crystal
We report the photoinduced ultrafast quasiparticle recombination dynamics of colossal magnetoresistance single crystal La1.2Sr1.8Mn2O7 by using femtosecond time-resolved reflection spectroscopy in a wide range of temperatures. Here, we find the transient reflectivity change ΔR exhibits a competition process of a fast negative component (∼ sub-picosecond) against a slow positive component (∼ nanosecond), as the sample goes from paramagnetic (PM) to ferromagnetic (FM) state with decreasing the temperature. The very fast initial decay of the photoinduced ΔR corresponds to the photoionization of the Jahn-Teller polaronic response, which is unambiguously sensitive to the coupling between electron and lattice in the PM and FM phases in La1.2Sr1.8Mn2O7 single crystal.
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