Hidden Fermi surface in K${}_x$Fe${}_{2-y}$Se${}_2$: LDA+DMFT study

Abstract

In this paper we provide theoretical LDA+DMFT support of recent ARPES experimental observation of the so called hidden hole like band and corresponding hidden Fermi surface sheet near $\Gamma$-point in the K${}_{0.62}$Fe${}_{1.7}$Se${}_2$ compound. To some extent this is a solution to the long-standing riddle of Fermi surface absence around $\Gamma$-point in the K${}_x$Fe${}_{2-y}$Se${}_2$ class of iron chalcogenide superconductors. In accordance with the experimental data Fermi surface was found near the $\Gamma$-point within LDA+DMFT calculations. Based on the LDA+DMFT analysis in this paper it is shown that the largest of the experimental Fermi surface sheets is actually formed by a hybrid Fe-3d($xy,xz,yz$) quasiparticle band. It is also shown that the Fermi surface is not a simple circle as DFT-LDA predicts, but has (according to the LDA+DMFT) a more complicated `propeller'-like structure due to correlations and multiorbital nature of the K${}_x$Fe${}_{2-y}$Se${}_2$ materials. While the smallest experimental Fermi surface around $\Gamma$-point is in some sense fictitious, since it is formed by the summation of the intensities of the spectral function associated with `propeller' loupes and is not connected to any of quasiparticle bands.

4 pages, 4 figures

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