Scaling of the Fano Effect of the In-Plane Fe-As Phonon and the Superconducting Critical Temperature in Ba1−xKxFe2As2

B. Xu, E. Cappelluti, L. Benfatto, B. P. P. Mallett, P. Marsik, E. Sheveleva, F. Lyzwa, Th. Wolf, R. Yang, X. G. Qiu, Y. M. Dai, H. H. Wen, R. P. S. M. Lobo, and C. Bernhard
Phys. Rev. Lett. 122, 217002 – Published 29 May 2019
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    Abstract

    By means of infrared spectroscopy, we determine the temperature-doping phase diagram of the Fano effect for the in-plane Fe-As stretching mode in Ba1−xKxFe2As2. The Fano parameter 1/q2, which is a measure of the phonon coupling to the electronic particle-hole continuum, shows a remarkable sensitivity to the magnetic and structural orderings at low temperatures. Most strikingly, at elevated temperatures in the paramagnetic tetragonal state we observe a linear correlation between 1/q2 and the superconducting critical temperature Tc. Based on theoretical calculations and symmetry considerations, we identify the relevant interband transitions that are coupled to the Fe-As mode. In particular, we show that a sizable xy orbital component at the Fermi level is fundamental for the Fano effect and, thus, possibly also for the superconducting pairing.

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    • Received 18 October 2018

    DOI:https://doi.org/10.1103/PhysRevLett.122.217002

    © 2019 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Electron-phonon couplingSuperconductivity
    1. Physical Systems
    Iron-based superconductorsPnictides
    1. Techniques
    Reflectivity
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    B. Xu1,*, E. Cappelluti2, L. Benfatto3, B. P. P. Mallett1,4, P. Marsik1, E. Sheveleva1, F. Lyzwa1, Th. Wolf5, R. Yang6, X. G. Qiu6, Y. M. Dai7, H. H. Wen7, R. P. S. M. Lobo8,9, and C. Bernhard1,†

    • 1University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
    • 2Istituto di Struttura della Materia, CNR, 34149 Trieste, Italy
    • 3ISC-CNR and Department of Physics, Sapienza University of Rome, P. le A. Moro 5, 00185 Rome, Italy
    • 4The Photon Factory, Department of Physics, University of Auckland, 38 Princes Street, Auckland 1010, New Zealand
    • 5Institute of Solid State Physics, Karlsruhe Institute of Technology, Postfach 3640, Karlsruhe 76021, Germany
    • 6Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
    • 7National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
    • 8LPEM, ESPCI Paris, PSL University, CNRS, F-75005 Paris, France
    • 9Sorbonne Université, CNRS, LPEM, F-75005 Paris, France

    • *bing.xu@unifr.ch
    • †christian.bernhard@unifr.ch

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    Vol. 122, Iss. 21 — 31 May 2019

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