Optical conductivity of superconducting Rb2Fe4Se5

A. Charnukha; J. Deisenhofer; D. Pröpper; M. Schmidt; Z. Wang; Y. Goncharov; A. N. Yaresko; V. Tsurkan; B. Keimer; A. Loidl; A. V. Boris

doi:10.1103/physrevb.85.100504

arXiv · 1108.5698

Optical conductivity of superconducting Rb2Fe4Se5

A. Charnukha·J. Deisenhofer·D. Pröpper·M. Schmidt·Z. Wang·Y. Goncharov·A. N. Yaresko·V. Tsurkan·B. Keimer·A. Loidl·A. V. Boris

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Abstract

We report the complex dielectric function of high-quality nearly-stoichiometric Rb2Fe4Se5 (RFS) single crystals with Tc=32 K determined by wide-band spectroscopic ellipsometry and time-domain transmission spectroscopy in the spectral range 1 meV<=$\hbar$ω<=6.5 eV at temperatures 4 K<=T<=300 K. This compound simultaneously displays a superconducting and a semiconducting optical response. It reveals a direct band-gap of 0.45 eV determined by a set of spin-controlled interband transitions. Below 100 K we observe in the lowest THz spectral range a clear metallic response characterized by the negative dielectric permittivity ε1 and bare (unscreened) ωpl=100 meV. At the superconducting transition this metallic response exhibits a signature of a superconducting gap below 8 meV. Our findings suggest a coexistence of superconductivity and magnetism in this compound as two separate phases.

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A. Charnukha, J. Deisenhofer, D. Pröpper, M. Schmidt, Z. Wang, Y. Goncharov, A. N. Yaresko, V. Tsurkan, B. Keimer, A. Loidl, A. V. Boris. 2011-08-29. Optical conductivity of superconducting Rb2Fe4Se5. https://doi.org/10.1103/physrevb.85.100504

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