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| VOLUME 88 | ISSUE 10 |
PAGE 777
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| Electronic Structure of New AFFeAs Prototype of Iron Arsenide Superconductors |
I. A. Nekrasov, Z. V. Pchelkina*, M. V. Sadovskii
Institute Electrophysics RAS, 620016 Ekaterinburg, Ural Division, Russia
*Institute Metal Physics RAS, 620041 Ekaterinburg GSP-170, Ural Division, Russia
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PACS: 71.20.-b, 74.25.Jb, 74.70.Dd, 74.70.-b
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Abstract
This work is provoked by recent discovery of new class prototype
systems AFFeAs (A=Sr,Ca) of novel layered ironpnictide High-Tc
superconductors (Tc=36 K). Here we report ab initio LDA results for
electronic structure of the AFFeAs systems. We provide detailed comparison
between electronic properties of both new systems and reference LaOFeAs (La111) compound.
In the vicinity of the Fermi level all three systems have essentially the same
band dispersions. However for iron fluoride systems F(2p) states were
found to be separated in energy from As(4p) ones in contrast to La111,
where O(2p) states strongly overlaps with As(4p).
Thus it should be more plausible to include only Fe(3d) and As(4p) orbitals
into a realistic noninteracting model than for La111.
Moreover Sr substitution with smaller ionic radius Ca in AFFeAs materials
leads to a lattice contruction and stronger Fe(3d)-As(4p)
hybridization resulting in smaller value of the density of states
at the Fermi level in the case of Ca compound.
So to some extend Ca system reminds RE111 with later Rare Earths.
However Fermi surface of new fluorides is found to be nearly perfect
two-dimensional. Also we do not expect strong dependence of superconducting
properties with respect to different types of A substitutes.
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