On the origin of the shallow and "replica" bands in FeSe monolayer superconductors1)
I. A. Nekrasov+ 1), N. S. Pavlov+ 2), M. V. Sadovskii+* 2)
+Institute of Electrophysics, Russian Academy of Sciences, Ural Branch, 620016 Ekaterinburg, Russia
*M.N. Mikheev Institute of Metal Physics, Russian Academy of Sciences, Ural Branch, 620290 Ekaterinburg, Russia
We compare electronic structures of single FeSe layer films on
SrTiO3 substrate (FeSe/STO) and KxFe2-ySe2 superconductors
obtained from extensive LDA and LDA+DMFT calculations with the results of
It is demonstrated that correlation effects on Fe-3d states are sufficient
in principle to explain the formation of the shallow electron-like bands
the M(X)-point. However, in FeSe/STO these effects alone are apparently
insufficient for the simultaneous elimination of the hole-like Fermi
around the Γ-point which is not observed in ARPES experiments.
Detailed comparison of ARPES detected and calculated quasiparticle bands
reasonable agreement between theory and experiment. Analysis of the bands
with respect to their origin and orbital composition shows, that
for FeSe/STO system the experimentally observed "replica" quasiparticle
at the M-point (usually attributed to forward scattering interactions with
optical phonons in SrTiO3 substrate) can be reasonably understood just as
LDA calculated Fe-3dxy band, renormalized by electronic correlations.
The only manifestation of the substrate reduces to lifting the degeneracy
between Fe-3dxz and Fe-3dyz bands in the vicinity of M-point.
For the case of KxFe2-ySe2 most bands
observed in ARPES can also be understood as correlation renormalized Fe-3d
calculated bands, with overall semi-quantitative agreement with LDA+DMFT