Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.24: Poster

Monday, March 22, 2010, 14:00–18:00, Poster A

Electrodynamics of electron doped iron-pnictide superconductors Ba(Fe_1−xM_x)₂As₂ — •Dan Wu¹, Neven Barisic¹, Natalia Drichko¹, Boris Gorshunov¹, Philipp Kallina¹, Martin Dressel¹, Linjun Li², Xiao Lin², Guanghan Cao², and Zhu-an Xu² — ¹1. Physikalisches Institut, Universiät Stuttgart, Germany — ²Department of Physics, Zhejiang University, People’s Republic of China

The temperature dependence of the ab-plane optical reflectivity of Ba(Fe_0.92Co_0.08)₂As₂ and Ba(Fe_0.95Ni_0.05)₂As₂ single crystals is measured in a wide spectral range. In the metallic state, the optical conductivity consists of a broad incoherent background and a narrow Drude-like component which determines the transport properties; only the latter contribution strongly depends on the composition and temperature. Upon entering the superconducting regime, the conductivity below 100 cm⁻¹ drops due to the complete opening a gap in the density of states at 2Δ/k_BT_c≈ 2.5−3. From the analysis of the complex conductivity spectra we obtain the penetration depth λ=(3500± 350) Å for Ba(Fe_0.92Co_0.08)₂As₂ and (3000± 300) Å for Ba(Fe_0.95Ni_0.05)₂As₂. The calculated superfluid density ρ_s of both compounds nicely fits the scaling relation ρ_s=(125± 25)σ_dcT_c.