We describe the results of x-ray fluorescence holography (XFH) measurements of $1T^{\prime }\text{−}{\mathrm{TaTe}}_2$, in which Ta ribbon clusters that appear at high temperatures change to heptamers at low temperatures. It was previously thought that the ribbon cluster in the high-temperature phase was composed of multiple linear trimers formed by three-center two-electron $\sigma$ bonds, but recent structural studies have revealed that the Ta atoms at the trimer centers are slightly displaced in the direction of the chain extension. Since it is thought that this local displacement is ordered to form a low-temperature heptamer, elucidating the origin of the local displacement is an important issue. Our XFH measurements revealed that there is no attractive interaction between the Ta atoms that are locally displaced, but rather there is a repulsive interaction. This indicates that the origin of the heptamer formation is not due to cluster formation such as a charge density wave occurring in the direction of the chain extension. We discuss that the origin of the local atomic displacement is the formation of random dimers between different Ta sites.

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• Crystal phenomena
• Lattice dynamics
• Molecular magnetism
• Phase transitions
• Spin dynamics
• 2-dimensional systems
• Crystal structures
• Layered crystals
• Strongly correlated systems
• Transition metal dichalcogenides
• X-ray diffraction
• X-ray fluorescence holography