Abstract
Photoexcited quasiparticle relaxation dynamics are investigated in a superconductor as a function of doping δ and temperature using ultrafast time-resolved optical spectroscopy. A model calculation is presented that describes the temperature dependence of the photoinduced quasiparticle population photoinduced transmission and relaxation time τ for three different superconducting gaps: (i) a temperature-dependent collective gap such that as (ii) a temperature-independent gap, which might arise for the case of a superconductor with preformed pairs, and (iii) an anisotropic (e.g., -wave) gap with nodes. Comparison of the theory with data of photoinduced transmission reflection and quasiparticle recombination time τ in over a very wide range of doping is found to give good quantitative agreement with a temperature-dependent BCS-like isotropic gap near optimum doping and a temperature-independent isotropic gap in underdoped A pure -wave gap was found to be inconsistent with the data.
- Received 11 February 1998
DOI:https://doi.org/10.1103/PhysRevB.59.1497
©1999 American Physical Society