title: Nematic Resonance in the Raman Response of Iron-Based Superconductors.
abstract: In a fully gapped superconductor the electronic Raman response has a pair-breaking peak at twice the superconducting gap Δ, if the Bogoliubov excitations are uncorrelated. Motivated by the iron based superconductors, we study how this peak is modified if the superconducting phase hosts a nematic-structural quantum critical point. We show that, upon approaching this point by tuning, e.g., doping, the growth of nematic correlations between the quasiparticles transforms the pair-breaking peak into a nematic resonance. The mode energy is below 2Δ, and stays finite at the quantum critical point, where its spectral weight is sharply enhanced. The latter is consistent with recent experiments on electron-doped iron based superconductors and provides direct evidence of nematic correlations in their superconducting phases.
authors.affiliation: Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Gallais
authors.affiliation: Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: Indranil
authors.initials: I
authors.lastname: Paul
authors.affiliation: Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France.
authors.forename: Ludivine
authors.initials: L
authors.lastname: Chauvière
authors.affiliation: Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.|Institute for Solid State Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Schmalian