Experimental confirmation of the magnetic ordering transition induced by an electronic structure change in the metallic triangular antiferromagnet Co$_{1/3}$TaS$_2$

TL;DR

This study combines ARPES experiments with DFT+DMFT calculations to confirm that electronic structure changes induce a magnetic ordering transition in the metallic triangular antiferromagnet Co$_{1/3}$TaS$_2$, revealing the link between Fermi surface topology and magnetic phases.

Contribution

The paper provides the first combined experimental and theoretical evidence that electronic structure modifications drive magnetic ordering transitions in Co$_{x}$TaS$_2$.

Findings

Fermi surface maps match the triple-Q state with nesting vectors.

New electron pocket appears at K in Co$_{0.340}$TaS$_2$ due to correlation effects.

Magnetic susceptibility calculations align with observed phase transition at x=1/3.

Abstract

We report ARPES studies combined with DFT+DMFT calculations to confirm that the magnetic ordering vector transition from \textbf{Q}=(1/2,0,0) to \textbf{Q}=(1/3,0,0) in the metallic triangular antiferromagnets Co$_{1/3\pm\epsilon}$TaS$_2$ ($\epsilon\approx$0.007) is induced by the electronic structure change in the system. The ARPES-measured Fermi surface (FS) maps of Co$_{0.325}$TaS$_2$ show two hexagonal and one circular hole-like FSs around $\Gamma$, which matches well with the triple-\textbf{Q} state by taking into account the contribution of nesting vectors occurring between Co 3$d$ and Ta 5$d$ orbitals. In the case of Co$_{0.340}$TaS$_2$, a new electron pocket around K appears and the FS geometry changes as a result of the correlation effect of Co$_4$S$_{18}$ tripods forming in the system. The magnetic susceptibility calculations based on the charge-self-consistent DFT+DMFT band structures and the random phase approximation indicate that the most stable magnetic ordering vector (1/2,0,0) split into (1/6,0,0) and (1/2,0,0), which is consistent with the magnetic phase transition around $x$=1/3 in Co$_{x}$TaS$_2$.