Dimer Mott Insulator in an Oxide Heterostructure

TL;DR

This paper proposes a method to engineer a dimer Mott insulator in oxide heterostructures, demonstrating its stability and magnetic properties through computational studies, advancing the design of correlated electronic states.

Contribution

It introduces a novel approach to create a dimer Mott insulator in oxide heterostructures using ionic discontinuity doping and confirms its stability via ab initio and model calculations.

Findings

Dimer Mott insulator can be realized with a single SrO layer in GdTiO3.

The state is stable, ferromagnetic, with a bonding/anti-bonding splitting of ~0.65 eV.

The Mott gap size depends on the Hubbard U parameter.

Abstract

We study the problem of designing an artificial Mott insulator in a correlated oxide heterostructure. We consider the extreme limit of quantum confinement based on ionic discontinuity doping, and argue that a unique dimer Mott insulator can be achieved for the case of a single SrO layer in a GdTiO$_3$ matrix. In the dimer Mott insulator, electrons are localized not to individual atoms but to bonding orbitals on molecular dimers formed across a bilayer of two TiO$_2$ planes, and is analogous to the Mott insulating state of Hubbard ladders, studied in the 1990s. We verify the existence of the dimer Mott insulator through both ab initio and model Hamiltonian studies, and find for reasonable values of Hubbard $U$ that it is stable and ferromagnetic with a clear bonding/anti-bonding splitting of order 0.65eV, and a significant smaller Mott gap whose size depends upon $U$. The combined effects of polar discontinuity, strong structural relaxation and electron correlations all contribute to the realization of this unique ground state.