Quasi-High-Pressure Effects in Transition-Metal-Rich Dichalcogenide, Hf₃Te₂

High pressure offers an intriguing avenue for the change in physical and chemical properties of condensed matters such as superconductivity, structural phase transition, and catalytic activity. However, it is hard to achieve the high-pressure phases of elements and compounds in an ambient condition by chemical pressure due to the limitation in bonding length variation. Here, we report the quasi-high-pressure state of Hf cuboid confined between two-dimensional chalcogen layers in transition-metal-rich dichalcogenide of Hf₃Te₂, exhibiting the enhanced degree of localization and chemical potential for valence electrons compared to ambient Hf elements. The structural analysis reveals that Hf metals in Hf₃Te₂ form a local cuboid structure, in which the coordination for central Hf is identical to that of high-pressure body-centered-cubic Hf phase. Density functional theory calculations verify that the compressed cuboid in Hf₃Te₂ has a key role for an abnormal heat capacity beyond Dulong-Petit limit and reduced work function, resulting from the intrinsic pressure induced s-d transfer in covalent electrons between Hf-Hf bonding. This transition-metal-rich dichalcogenide can guide a route to realize a high-pressure element under ambient condition and offer an opportunity to explore a new layered two-dimensional material.