Electron-lattice instabilities suppress cuprate-like electronic structures in SrFeO$_3$/SrTiO$_3$ superlattices

TL;DR

This study uses ab initio density functional theory to investigate how electron-lattice instabilities in SrFeO3/SrTiO3 superlattices suppress cuprate-like electronic structures, revealing that lattice distortions lead to insulating behavior.

Contribution

It demonstrates that electron-lattice instabilities in these superlattices prevent the formation of cuprate-like electronic structures, highlighting the role of lattice effects in electronic properties.

Findings

Insulating SrTiO3 spacer layers significantly alter SrFeO3 electronic behavior.

Single SrFeO3 layers exhibit a two-dimensional, nested Fermi surface similar to cuprates.

Jahn-Teller instability coupled with octahedral tilt modes induces insulating states.

Abstract

Using {\it ab initio} density functional theory we explore the behavior of thin layers of metallic $d^4$ SrFeO$_3$ confined between the $d^0$ dielectric SrTiO$_3$ in a superlattice geometry. We find the presence of insulating SrTiO$_3$ spacer layers strongly affects the electronic properties of SrFeO$_3$: For single SrFeO$_3$ layers constrained to their bulk cubic structure, the Fermi surface is two-dimensional, nested and resembles the hole-doped superconducting cuprates. A Jahn-Teller instability couples to an octahedral tilt mode, however, to remove this degeneracy resulting in insulating superlattices.