Quasiparticle relaxation dynamics in superconductors with different gap structures: theory and experiments on YBa_{2}Cu_{3}O_{7-δ}

V. V. Kabanov; J. Demsar; B. Podobnik; D. Mihailovic

doi:10.1103/PhysRevB.59.1497

paper

Quasiparticle relaxation dynamics in superconductors with different gap structures: theory and experiments on YBa_{2}Cu_{3}O_{7-δ}

arXiv:cond-mat/9809333 · doi:10.1103/PhysRevB.59.1497

Abstract

Photoexcited quasiparticle relaxation dynamics are investigated in a $Y B a_{2} C u_{3} O_{7 - δ}$ superconductor as a function of doping $δ$ and temperature $T$ using ultrafast time-resolved optical spectroscopy. A model calculation is presented which describes the temperature dependence of the photoinduced quasiparticle population $n_{p e}$ , photoinduced transmission $Δ T / T$ and relaxation time $τ$ for three different superconducting gaps: (i) a temperature-dependent collective gap such that $Δ (T) \to 0$ as $T \to T_{c}$ , (ii) a temperature-independent gap, which might arise for the case of a superconductor with pre-formed pairs and (iii) an anisotropic (e.g. d-wave) gap with nodes. Comparison of the theory with data of photoinduced transmission $∣Δ T / T ∣$ , reflection $∣ D e l t a R / R ∣$ and quasiparticle recombination time $τ$ in $Y B a_{2} C u_{3} O_{7 - δ}$ over a very wide range of doping ( $0.1 < δ < 0.48)$ is found to give good quantitative agreement with a temperature-dependent BCS-like isotropic gap near optimum doping ( $δ < 0.1)$ and a temperature-independent isotropic gap in underdoped $Y B a_{2} C u_{3} O_{7 - δ}$ ( $0.15 < δ < 0.48$ ). A pure d-wave gap was found to be inconsistent with the data.

12 pages, 7 ps figures, to be published in Phys. Rev. B

Quasiparticle relaxation dynamics in superconductors with different gap structures: theory and experiments on YBa_{2}Cu_{3}O_{7-δ}

Abstract

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