  Motivated by the recent low-tempearture experiments on bulk FeSe, we study
the electron correlation effects in a multiorbital model for this compound in
the nematic phase using the U(1) slave-spin theory. We find that a finite
nematic order helps to stabilize an orbital selective Mott phase. Moreover, we
propose that when the d- and s-wave bond nematic orders are combined with the
ferro-orbital order, there exists a surprisingly large orbital selectivity
between the xz and yz orbitals even though the associated band splitting is
relatively small. Our results explain the seemingly unusual observation of
strong orbital selectivity in the nematic phase of FeSe, and uncover new clues
on the nature of the nematic order, and sets the stage to elucidate the
interplay between superconductivity and nematicity in iron-based
superconductors.
