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arXiv · 1508.05016

Suppression of orbital ordering by chemical pressure in FeSe1-xSx

M. D. Watson·T. K. Kim·A. A. Haghighirad·S. F. Blake·N. R. Davies·M. Hoesch·T. Wolf·A. I. Coldea
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Abstract

We report a high-resolution angle-resolved photo-emission spectroscopy study of the evolution of the electronic structure of FeSe1-xSx single crystals. Isovalent S substitution onto the Se site constitutes a chemical pressure which subtly modifies the electronic structure of FeSe at high temperatures and induces a suppression of the tetragonal-symmetry-breaking structural transition temperature from 87K to 58K for x=0.15. With increasing S substitution, we find smaller splitting between bands with dyz and dxz orbital character and weaker anisotropic distortions of the low temperature Fermi surfaces. These effects evolve systematically as a function of both S substitution and temperature, providing strong evidence that an orbital ordering is the underlying order parameter of the structural transition in FeSe1-xSx. Finally, we detect the small inner hole pocket for x=0.12, which is pushed below the Fermi level in the orbitally-ordered low temperature Fermi surface of FeSe.

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M. D. Watson, T. K. Kim, A. A. Haghighirad, S. F. Blake, N. R. Davies, M. Hoesch, T. Wolf, A. I. Coldea. 2015-08-20. Suppression of orbital ordering by chemical pressure in FeSe1-xSx. https://doi.org/10.1103/physrevb.92.121108

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