The momentum distribution of the energy gap opening at the Fermi level of superconductors is a direct fingerprint of the pairing mechanism. While the phase diagram of the iron-based superconductors promotes antiferromagnetic fluctuations as a natural candidate for electron pairing, the precise origin of the interaction is highly debated. We used angle-resolved photoemission spectroscopy to reveal directly the momentum distribution of the superconducting gap in FeTe1-xSex, which has the simplest structure of all iron-based superconductors. We found isotropic superconducting gaps on all Fermi surfaces whose sizes can be fitted by a single gap function derived from a strong coupling approach, strongly suggesting local antiferromagnetic exchange interactions as the pairing origin.
@article{arxiv.1107.0985,
title = {Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45},
author = {H. Miao and P. Richard and Y. Tanaka and K. Nakayama and T. Qian and K. Umezawa and T. Sato and Y. -M. Xu and Y. -B. Shi and N. Xu and X. -P. Wang and P. Zhang and H. -B. Yang and Z. -J. Xu and J. S. Wen and G. -D. Gu and X. Dai and J. -P. Hu and T. Takahashi and H. Ding},
journal= {arXiv preprint arXiv:1107.0985},
year = {2012}
}