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

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 sensitivit...

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Bibliographic Details
Published in:Physical review letters 2019-05, Vol.122 (21), p.1
Main Authors: Xu, B, Cappelluti, E, Benfatto, L, Mallett, B P P, Marsik, P, Sheveleva, E, Lyzwa, F, Wolf, Th, Yang, R, Qiu, X G, Dai, Y M, Wen, H H, Lobo, R P S M, Bernhard, C
Format: Article
Language:English
Subjects:
Coupled modes
Critical temperature
High temperature
Phase diagrams
Phonons
Superconductivity
Transition temperature
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Summary: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.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.122.217002