Effect of ordering of mobile oxygen on spectra of two-magnon and electronic Raman scattering of light in YBa_2Cu_3O_(6+x) crystals with different doping levels

摘要

The effect of ordering of mobile chain-site oxygen in YBa_2Cu_3O_(6+x) crystals at different doping levels x on the kinetics of the intensity change of the two-magnon line and the extended structureless electronic continuum in optical Raman spectra and on the superconducting transition temperature T_c, has been studied in detail. An increase in the chain-site oxygen content x leads to a higher contribution of free carriers to the electronic continuum in Raman spectra. The kinetics of the electronic continuum becomes slower with x, whereas the relaxation rate of the two-magnon scattering is a nonmonotonic function of the stoichiometric index. Computer simulations of the relaxation of nonequilibrium states using the Monte Carlo technique qualitatively describe the kinetics observed in experiments. Our results lead us to a conclusion about local inhomogeneities in the electronic and spin systems in CuO_2 planes with scales of several lattice constants.