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Momentum Dependence of the Nematic Order Parameter in Iron-Based Superconductors.

  • Author(s): Pfau, H
  • Chen, SD
  • Yi, M
  • Hashimoto, M
  • Rotundu, CR
  • Palmstrom, JC
  • Chen, T
  • Dai, P-C
  • Straquadine, J
  • Hristov, A
  • Birgeneau, RJ
  • Fisher, IR
  • Lu, D
  • Shen, Z-X
  • et al.
Abstract

The momentum dependence of the nematic order parameter is an important ingredient in the microscopic description of iron-based high-temperature superconductors. While recent reports on FeSe indicate that the nematic order parameter changes sign between electron and hole bands, detailed knowledge is still missing for other compounds. Combining angle-resolved photoemission spectroscopy with uniaxial strain tuning, we measure the nematic band splitting in both FeSe and BaFe_{2}As_{2} without interference from either twinning or magnetic order. We find that the nematic order parameter exhibits the same momentum dependence in both compounds with a sign change between the Brillouin center and the corner. This suggests that the same microscopic mechanism drives the nematic order in spite of the very different phase diagrams.

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