Femtosecond quasiparticle relaxation dynamics and probe polarization anisotropy in YBa2Cu4O8

摘要

Femtosecond pump probe experiments are reported on quasiparticle relaxationand recombination in YBa2Cu4O8 as a function of temperature and polarization.The data show a 2-component relaxation similar to YBa2Cu3O7-\delta, onecomponent being assocated with the superconducting transition, and the otherwith the pseudogap below T* The relaxation time tau_p associated with thepseudogap is found to be T-independent, while the relaxation time tau_g of thecomponent obseved only below Tc exhibits a clear divergence near Tc. A strongpolarisation anisotropy of the picosecond transient is observed below Tc whichis attributed to the anisotropy of the probe transition matrix elements.