Role of incipient bands in Fe-based superconductors
Superconductivity is normally considered to be a Fermi surface phenomenon, since
the usual phonon mediated interaction is attractive only over a small energy
range near the Fermi level. If a band does not cross the Fermi energy but
is nevertheless within this attractive range, we call it "incipient".
In the case of a single band, it has been known for many years that
to the critical temperature from incipient bands are very weak. In the
paper below, we showed that in other cases where the pairing arises primarily
from other bands at the Fermi level, the presence of an incipient band can
substantially assist Tc
, and lead to large gaps on incipient bands.
This includes typical bulk Fe-based system
like LiFeAs, where a significant gap on an incipient band has been seen
experimentally, and more unusual systems like FeSe monolayers on strontium
titanate, where a substrate phonon may provide part of the attractive
"Electron pairing in the presence of incipient bands in iron-based
superconductors", Xiao Chen, S. Maiti, A.
Linscheid, and P. J. Hirschfeld, arXiv:1508.04782, to be published in Phys.
Bootstrapping of phonon-mediated transition temperature Tph
by spin fluctuation interaction arising from incipient hole band with
band extremum E g
. Actual Tc
can be many times