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Distinctive orbital anisotropy observed in the nematic state of a FeSe thin film

  • Author(s): Zhang, Y;
  • Yi, M;
  • Liu, ZK;
  • Li, W;
  • Lee, JJ;
  • Moore, RG;
  • Hashimoto, M;
  • Nakajima, M;
  • Eisaki, H;
  • Mo, SK;
  • Hussain, Z;
  • Devereaux, TP;
  • Shen, ZX;
  • Lu, DH
  • et al.
Abstract

The nematic state, where a system is translationally invariant but breaks rotational symmetry, has drawn great attention recently due to the experimental observations of such a state in both cuprates and iron-based superconductors. The origin of nematicity and its possible tie to the pairing mechanism of high-Tc, however, still remain controversial. Here, we study the electronic structure of a multilayer FeSe film using angle-resolved photoemission spectroscopy. The band reconstruction in the nematic state is clearly delineated. We find that the energy splitting between dxz and dyz bands shows a nonmonotonic distribution in momentum space. From the Brillouin zone center to the Brillouin zone corner, the magnitude of splitting first decreases, then increases, and finally reaches the maximum value of ∼70 meV. Moreover, besides the dxz and dyz bands, band splitting was also observed on the dxy bands with a comparable energy scale around 45 meV. Our results suggest that the electronic anisotropy in the nematic state cannot be explained by a simple on-site ferro-orbital order. Instead, strong anisotropy exists in the hopping of all dxz,dyz, and dxy orbitals, the origin of which holds the key to a microscopic understanding of the nematicity in iron-based superconductors.

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