Time-resolved optical response in BSCCO-2212

The dynamics of the optical response of BSCCO-2212 measured at 1.5 eV has been investigated using femtosecond spectroscopy. The temperature dependence of the response shows three distinct regimes: (1) T less than Tc: with increasing temperature the differential reflectance, (Delta) R/R greater than 0, decreases to zero at Tc, similar to the behavior of the BCS gap function, and the relaxation rate increases linearly with temperature. (2) Tc less than T less than T* (T* - Tc approximately 35 K): (Delta) R/R less than 0. (3) T greater than T*: a weak, positive (Delta) R/R response is measured in the metallic phase. The intermediate regime observed here coincides with the pseudo gap phase detected in ARPES measurements.