Discovery of Charge Order in the Transition Metal Dichalcogenide Fe$_{x}$NbS$_2$

TL;DR

This paper reports the discovery of a charge order phase in Fe-intercalated NbS2, revealing a new magnetic and electronic state driven by excess Fe atoms and magnetoelastic coupling, unique among intercalated TMDs.

Contribution

It presents the first observation of charge order in intercalated TMDs, linking charge and magnetic order via magnetoelastic coupling, and highlights the role of electronic correlations in stabilizing charge modulation.

Findings

Discovery of charge order in Fe$_{x}$NbS$_2$ with excess Fe

Charge order correlates with magnetic ordering temperatures

Charge modulation stabilized by electronic correlations

Abstract

The Fe intercalated transition metal dichalcogenide (TMD), Fe$_{1/3}$NbS$_2$, exhibits remarkable resistance switching properties and highly tunable spin ordering phases due to magnetic defects. We conduct synchrotron X-ray scattering measurements on both under-intercalated ($x$ = 0.32) and over-intercalated ($x$ = 0.35) samples. We discover a new charge order phase in the over-intercalated sample, where the excess Fe atoms lead to a zigzag antiferromagnetic order. The agreement between the charge and magnetic ordering temperatures, as well as their intensity relationship, suggests a strong magnetoelastic coupling as the mechanism for the charge ordering. Our results reveal the first example of a charge order phase among the intercalated TMD family and demonstrate the ability to stabilize charge modulation by introducing electronic correlations, where the charge order is absent in bulk 2H-NbS$_2$ compared to other pristine TMDs.