Orbital Selectivity Enhanced by Nematic Order in FeSe

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Bulk iron selenide (FeSe) exhibits a nematic phase at low temperatures, characterized by distinct electronic properties.
• Understanding electron correlation effects is crucial for explaining the behavior of FeSe in its nematic state.

Purpose of the Study:

• To investigate electron correlation effects in the nematic phase of FeSe using a multiorbital model.
• To explore the role of nematic order in stabilizing specific electronic phases.
• To elucidate the origin of strong orbital selectivity observed in FeSe.

Main Methods:

• Utilized the U(1) slave-spin theory, a sophisticated theoretical framework for studying electron correlations.
• Employed a multiorbital model tailored for the electronic structure of FeSe.
• Analyzed the interplay between different types of nematic orders (d- and s-wave bond, ferro-orbital).

Main Results:

• A finite nematic order was found to stabilize an orbital selective Mott phase in FeSe.
• A combination of d- and s-wave bond nematic orders with ferro-orbital order leads to significant orbital selectivity between xz and yz orbitals.
• This selectivity persists despite relatively small underlying band splitting.

Conclusions:

• The study explains the observed strong orbital selectivity in the nematic phase of FeSe.
• The findings provide new insights into the nature of nematic order in iron-based superconductors.
• This work lays the foundation for understanding the coupling between superconductivity and nematicity in these materials.