# Scaling of the Fano effect of the in-plane Fe-As phonon and the superconducting critical temperature in ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$

• Xu, Bing University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Fribourg, Switzerland
• Cappelluti, E. Istituto di Struttura della Materia, Trieste, Italy
• Benfatto, Larra ISC-CNR and Department of Physics, Sapienza University of Rome, Italy
29.05.2019
Published in:
• Physical Review Letters. - 2019, vol. 122, no. 21, p. 217002
English 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.
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
• English
Classification
Physics