Staggered FeSe Monolayer on SrTiO$_3$ (110) surface

TL;DR

This study explores how strain and lattice staggering in FeSe monolayers on SrTiO$_3$ (110) influence electronic, magnetic, and topological properties, revealing potential for topologically nontrivial phases without suppressing superconductivity.

Contribution

It demonstrates that strain-induced lattice staggering in FeSe monolayers can induce topological phases and modify magnetic frustration without harming superconductivity.

Findings

Strain causes lattice staggering and height differences in FeSe monolayer.

Strain elongates electron and hole pockets along specific directions.

Band inversion driven by strain indicates possible topological phases.

Abstract

We investigate the electronic and magnetic properties of FeSe monolayer on the anisotropic SrTiO$_3$ (110) surface. With compressive strain along $[1\bar{1}0]$ direction from the substrate, the monolayer FeSe possesses a staggered bipartite iron lattice with an height difference around 0.06\AA~ along the out-plane direction. The staggering causes stronger magnetic frustration between the collinear and checkerboard antiferromagnetic orders, and the strain elongates one electron and two hole pockets along the strain direction and the remaining hole pocket along the orthogonal direction. The strain-induced band splitting at $\Gamma$ can also result in a band inversion to drive the system into a topologically nontrivial phase. The absence of strong superconducting suppression on the staggered lattice suggests that the superconducting pairings may be insensitive to the modification of interactions and hopping parameters between two Fe sublattices.