Microscopic pairing fingerprint of the iron-based superconductor ${\rm Ba_{1-x}K_xFe_2As_2}$

Thomas Böhm; Florian Kretzschmar; Andreas Baum; Michael Rehm; Daniel Jost; Ramez Hosseinian Ahangharnejhad; Ronny Thomale; Christiam Platt; Thomas A. Maier; Werner Hanke; Brian Moritz; Thomas P. Devereaux; Douglas J. Scalapino; Saurabh Maiti; Peter J. Hirschfeld; Peter Adelmann; Thomas Wolf; Hai-Hu Wen; Rudi Hackl

arXiv · 1703.07749

Microscopic pairing fingerprint of the iron-based superconductor ${\rm Ba_{1-x}K_xFe_2As_2}$

Thomas Böhm·Florian Kretzschmar·Andreas Baum·Michael Rehm·Daniel Jost·Ramez Hosseinian Ahangharnejhad·Ronny Thomale·Christiam Platt·Thomas A. Maier·Werner Hanke·Brian Moritz·Thomas P. Devereaux·Douglas J. Scalapino·Saurabh Maiti·Peter J. Hirschfeld·Peter Adelmann·Thomas Wolf·Hai-Hu Wen·Rudi Hackl

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Abstract

Resolving the microscopic pairing mechanism and its experimental identification in unconventional superconductors is among the most vexing problems of contemporary condensed matter physics. We show that Raman spectroscopy provides an avenue for this quest by probing the structure of the pairing interaction at play in an unconventional superconductor. As we study the spectra of the prototypical Fe-based superconductor ${\rm Ba_{1-x}K_xFe_2As_2}$ for $0.22\le x \le 0.70$ in all symmetry channels, Raman spectroscopy allows us to distill the leading $s$-wave state. In addition, the spectra collected in the $B_{1g}$ symmetry channel reveal the existence of two collective modes which are indicative of the presence of two competing, yet sub-dominant, pairing tendencies of $d_{x^2-y^2}$ symmetry type. A comprehensive functional Renormalization Group (fRG) and random-phase approximation (RPA) study on this compound confirms the presence of the two sub-leading channels, and consistently matches the experimental doping dependence of the related modes. The synopsis of experimental evidence and theoretical modelling supports a spin-fluctuation mediated superconducting pairing mechanism.

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Thomas Böhm, Florian Kretzschmar, Andreas Baum, Michael Rehm, Daniel Jost, Ramez Hosseinian Ahangharnejhad, Ronny Thomale, Christiam Platt, Thomas A. Maier, Werner Hanke, Brian Moritz, Thomas P. Devereaux, Douglas J. Scalapino, Saurabh Maiti, Peter J. Hirschfeld, Peter Adelmann, Thomas Wolf, Hai-Hu Wen, Rudi Hackl. 2017-03-22. Microscopic pairing fingerprint of the iron-based superconductor ${\rm Ba_{1-x}K_xFe_2As_2}$. https://arxiv.org/abs/1703.07749

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