ULTRAFAST OPTICAL PROBES OF DYNAMIC BEHAVIOR IN LA _(0 . 7)SR_(0 . 3)MNO_3/YBA_2CU_3O_(7 - δ) /LA _(0 . 7)SR_(0 . 3)MNO_3 HETEROSTRUCTURE

摘要

Ultrafast pump-optical probe spectroscopy was used to analyze carriers dynamics behavior in La_(0.7)Sr_(0.3)MnO_3/YBa_2Cu_3O_(7-δ)/La_(0.7)Sr_(0.3)MnO_3 heterostructure. Our results show the pump signal ΔR/R for higher laser power (such as 21 and 41mW), below T c, first goes positive, then crosses zero and goes negative, before relaxing back to equilibrium over a time scale of a few ten picoseconds. We extract the characteristic relaxation time of the different process by fitting the data at these powers with a three-exponential decay. For higher laser power, the long characteristic relaxation time are obtained, which implies the competition between FM order and SC order in the La_(0.7)Sr_(0.3)MnO_3/YBa_2Cu_3O_(7-δ)/La_(0.7)Sr_(0.3)MnO_3 heterostructure.