Robust Mottness and tunable interlayer magnetism in Nb3X8 (X = F, Cl, Br, I) bilayers

TL;DR

This study uses DFT calculations to explore how interlayer coupling affects magnetic and Mott insulating properties in Nb3X8 bilayers, revealing tunable interlayer magnetism and robust Mott states across different stacking configurations.

Contribution

It provides the first detailed analysis of interlayer effects on magnetic and Mott properties in Nb3X8 bilayers, highlighting tunable interlayer magnetism.

Findings

Most bilayers are antiferromagnetic due to interlayer interactions.

Some configurations exhibit interlayer ferromagnetism, indicating tunability.

All studied bilayers maintain Mott insulating behavior.

Abstract

Kagome materials have attracted extensive attention due to their correlated properties. The breathing kagome material system Nb3X8 (X = F, Cl, Br, I) is regarded as a Mott insulator. However, studies on the influence of interlayer coupling on its magnetic and Mott properties are lacking. In this work, we investigated the effect of interlayer coupling on bilayer properties of each Nb3X8 (X = F, Cl, Br, I) compound via density functional theory (DFT) calculations, considering 24 stacking configurations per material. We found that each bilayer material is a Mott insulator. Due to the competition between interlayer Pauli repulsion and hopping, most interlayer magnetism is AFM, a small number of cases show AFM-FM degeneracy, and the magnetic ground state of 3 configurations is interlayer FM, i.e., tunable interlayer magnetism occurs. This robustness of Mott states coexisting with tunable interlayer magnetism provide novel and comprehensive analysis and insights for the research of breathing kagome Mott insulators.