Composition-dependent bulk properties of intercalated transition metal dichalcogenides $Co_{1/3(1\pm\delta)}NbS_{2}$

TL;DR

This study systematically investigates how varying cobalt composition in $Co_{1/3(1\u00b1\u03b4)}NbS_{2}$ affects its bulk electronic and magnetic properties, revealing tunable topological and magnetic phenomena.

Contribution

It provides the first detailed analysis of composition-dependent bulk properties and topological effects in intercalated transition metal dichalcogenides with precise cobalt control.

Findings

Topological Hall effect is suppressed when cobalt exceeds d=+4%

Longitudinal conductivity peaks before topological Hall effect disappears

Sommerfeld coefficients scale linearly with inverse Hall coefficient

Abstract

We report a systematic study of the composition-dependent bulk properties in $Co_{1/3(1\pm\delta)}NbS_{2}$ single crystals across a series of precisely controlled cobalt compositions with -4%<$\delta$<8%. By tuning the cobalt stoichiometry, we find that the topological Hall effect is critically sensitive to the intercalant cobalt composition and is completely suppressed when the cobalt composition exceeds $\delta$=+4%. We observe that the longitudinal conductivity is also strongly influenced by the cobalt composition, reaching its maximum value just before the disappearance of the topological Hall effect. Furthermore, heat capacity measurements reveal distinct Sommerfeld coefficients ($\gamma$) across different compositions, which exhibit a clear linear scaling with the inverse of the ordinary Hall coefficient ($R_H^{-1}$). These results demonstrate that composition tuning in $Co_{1/3(1\pm\delta)}NbS_{2}$ systematically modifies the low-energy electronic degree of freedom, moving beyond a simple dilute impurity picture. Finally, we use the microscopic spin Hamiltonian to explain the stability of experimentally observed M-point modulation vector and the corresponding triple-Q magnetic order. Our findings highlight that the topological properties of this system are highly tunable through precise control of the intercalant concentration, offering a new perspective on the competition between electronic and magnetic orders in intercalated transition-metal dichalcogenides.