Stacking effect and Coulomb correlation in layered charge density wave phase of 1T-NbS2

TL;DR

This study uses first-principles calculations to investigate how stacking configurations and electron-electron interactions influence the electronic and magnetic properties of layered 1T-NbS2 with charge density waves, revealing new insights into their interplay.

Contribution

It uncovers the significant impact of stacking order and Coulomb correlation on the electronic phases and magnetic states of 1T-NbS2, challenging the conventional Mott localization perspective.

Findings

Two stable stacking configurations identified: metallic single-layer and insulating paired-bilayer.

Coulomb interactions induce magnetic and metal-insulator transitions depending on stacking.

Stacking order critically influences electronic structure and magnetic properties.

Abstract

Based on first-principles calculations, we explored the interplay between stacking effect and electron-electron correlation in the layered vdW material of bulk 1T-NbS2 with a 2D charge density wave (CDW) order. Without considering the Coulomb correlation, two energetically favorable out-of-plane stacking configurations are identified: one is a metallic phase with a single-layer stacking pattern, another is a band insulator with a paired-bilayer stacking configuration. Even though the Coulomb correlation is taken into account, the two energetic favorable stacking orders are still far more stable than other stacking orders. Furthermore, increasing the Coulomb interaction, the paired-bilayer stacking configuration transforms from nonmagnetic band insulator to antiferromagnetic insulator, while the single-layer stacking undergoes a Slater-Mott metal-insulator transition, which indicates the non-negligible role of electron-electron correlation interactions. In addition, the electronic structure and magnetic ground state change drastically among different stacking configurations, providing a platform to tune the electronic structures and interlayer magnetic interactions by altering the stacking order. In contrast to the widely accepted scenario of Mott localization as the driving force behind the gap formation in the CDW phase of layered transition metal dichalcogenides, our results not only highlight the crucial role of stacking order in the electronic structures of 1T-NbS2, but also shed fresh light on the distinct effects of Coulomb interaction in different stacking arrangements.