Ultrafast relaxation in YBa 2Cu 3O 7− δ on the femtosecond scale: Luttinger or two-dimensional Fermi liquid picture?

Abstract

A method for probing Fermi liquid (FL) versus non-Fermi liquid (NFL) behavior in the normal state of high T c oxide-superconductors YBa 2Cu 3O 7− δ by femtosecond pump-supercontinuum probe spectroscopy is presented. The method is based on the determination of the spectral dependence of non-equilibrium charge carriers relaxation rate γ( ω probe ) in a wide spectral range of probing, ℏω probe =1.6–3.2 eV. It is shown that the relaxation rate decreases sharply for the optical transitions in the vicinity of the Fermi level E F, the position of the rate minimum pointing to the location of E F. The probe energy dependence of the relaxation rate around the minimum gives unique information on the damping rate of quasi-particles near the Fermi level and hence can resolve the FL versus NFL behavior. Deviations from the FL behavior in YBa 2Cu 3O 7− δ are observed and discussed.