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Far-infrared optical conductivity gap in superconducting MgB2 films

R. A. Kaindl·M. A. Carnahan·J. Orenstein·D. S. Chemla·H. M. Christen·H. Zhai·M. Paranthaman·D. H. Lowndes
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Abstract

We report the first study of the optical conductivity of MgB2 covering the range of its superconducting energy gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity of thin films. The imaginary part reveals an inductive reponse due to the emergence of the superconducting condensate. The real part exhibits a strong depletion of oscillator strength near 5 meV resulting from the opening of a superconducting energy gap. The gap ratio of 2Delta/kTc = 1.9 is well below the weak-coupling value, pointing to complex behavior in this novel superconductor

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R. A. Kaindl, M. A. Carnahan, J. Orenstein, D. S. Chemla, H. M. Christen, H. Zhai, M. Paranthaman, D. H. Lowndes. 2001-06-18. Far-infrared optical conductivity gap in superconducting MgB2 films. https://doi.org/10.1103/physrevlett.88.027003

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