Evidence for unidirectional nematic bond ordering in FeSe

Matthew D. Watson, Timur Kim, Luke Rhodes, Matthias Eschrig, Moritz Hoesch, A. A. Haghighirad, Amalia I. Coldea

Research output: Contribution to journalLetterpeer-review

98 Downloads (Pure)


The lifting of dxz-dyz orbital degeneracy is often considered a hallmark of the nematic phase of Fe-based superconductors, including FeSe, but its origin is not yet understood. Here we report a high resolution Angle-Resolved Photoemission Spectroscopy study of single crystals of FeSe, accounting for the photon-energy dependence and making a detailed analysis of the temperature dependence. We find that the hole pocket undergoes a fourfold-symmetry-breaking distortion in the nematic phase below 90K, but in contrast the changes to the electron pockets do not require fourfold symmetry-breaking. Instead, there is an additional separation of the existing dxy and dxz/yz bands - which themselves are not split within resolution. These observations lead us to propose a new scenario of "unidirectional nematic bond ordering" to describe the low-temperature electronic structure of FeSe, supported by a good agreement with 10-orbital tight binding model calculations.
Original languageEnglish
Article number201107(R)
Number of pages6
JournalPhysical Review B
Issue number20
Publication statusPublished - 11 Nov 2016

Cite this