Time-Resolved Optical Studies of Quasiparticle Dynamics in High-Temperature Superconductors Experiments and theory
Ultrafast time-resolved optical spectroscopy in high-temperature superconductors enables the direct real-time measurement of nonequilibrium quasiparticle recombination dynamics. In addition, it also gives detailed information about the symmetry of the superconducting gap and the “pseudogap”, their doping dependence and their temperature dependence. Experimental data, together with theoretical models on the photoinduced transmission amplitude and relaxation time as a function of temperature and doping in YBa 2Cu3O7-δ gives a consistent picture of the evolution of low-energy structure, where a temperature-independent gap is shown to exist in the underdoped state which evolves with doping into a two-component state near optimum doping, where the dominant response is from a T-dependent BCS-like superconducting gap.