Femtosecond quasiparticle relaxation dynamics and probe polarization anisotropy in YSrxBa2-xCu4O8 (x=0,0.4) -: art. no. 020510

Femtosecond pump probe experiments are reported on quasiparticle relaxation and recombination in YSrxBa2-xCu4O8 as a function of temperature and polarization. The data show a two-component relaxation similar to YBa2Cu3O7-delta, one component being associated with the superconducting transition, and the other with the pseudogap below T-*. The relaxation time tau(p) associated with the pseudogap is found to be T independent, while the relaxation time tau(G) of the component observed only below T-c exhibits a clear divergence near T-c. A strong polarization anisotropy of the picosecond transient is observed below T-c which is attributed to the anisotropy of the probe transition matrix elements.