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Evidence for unidirectional nematic bond ordering in FeSe

DOI: 10.1103/PhysRevB.94.201107 DOI Help

Authors: Matthew Watson (Diamond Light Source) , Timur Kim (Diamond Light Source) , Luke Rhodes (Royal Holloway, University of London, Diamond Light Source) , Matthias Eschrig (Royal Holloway, University of London) , Moritz Hoesch (Diamond Light Source) , Amir Haghighirad (University of Oxford) , Amalia Coldea (Clarendon Laboratory, Department of Physics, University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 94 , PAGES 201107

State: Published (Approved)
Published: November 2016
Diamond Proposal Number(s): 10203 , 11804 , 12799

Open Access Open Access

Abstract: The lifting of d xz -d yz 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 90~K, but in contrast the changes to the electron pockets do not require fourfold symmetry-breaking. Instead, there is an additional separation of the existing d xy and d xz/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.

Subject Areas: Physics, Materials

Instruments: I05-ARPES