Observation of an Orbital Selective Electron-Mode Coupling in Fe-Based High-$T_c$ Superconductors

TL;DR

This study uses angle-resolved photoemission spectroscopy to identify an orbital-dependent electron-mode coupling in Fe-based high-temperature superconductors, revealing an anomaly linked to unconventional electronic interactions and pairing symmetry.

Contribution

It reports the observation of an orbital selective mode coupling anomaly in Fe-based superconductors, suggesting an electronic origin and supporting anti-phase s-wave pairing symmetry.

Findings

Anomaly around 25 meV in dispersion vanishes above Tc

Mode energy is approximately 13 meV and depends on orbital and temperature

Results support an unconventional electronic pairing mechanism

Abstract

We have performed an angle-resolved photoemission spectroscopy study of the new superconductor Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ in the low energy range. We report the observation of an anomaly around 25 meV in the dispersion of superconducting Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ samples that nearly vanishes above $T_c$. The energy scale of the related mode (13$\pm$2 meV) and its strong dependence on orbital and temperature indicates that it is unlikely related to phonons. Moreover, the momentum locations of the kink can be connected by the antiferromagnetic wavevector. Our results point towards an unconventional electronic origin of the mode and the superconducting pairing in the Fe-based superconductors, and strongly support the anti-phase s-wave pairing symmetry.