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arXiv · 2207.11298

Precursor phase with full phonon softening above the charge-density-wave phase transition in $2H$-TaSe$_2$

Xingchen Shen·Rolf Heid·Roland Hott·Björn Salzmann·Marli dos Reis Cantarino·Claude Monney·Ayman H. Said·Bridget Murphy·Kai Rossnagel·Stephan Rosenkranz·Frank Weber
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Abstract

Research on charge-density-wave (CDW) ordered transition-metal dichalcogenides continues to unravel new states of quantum matter correlated to the intertwined lattice and electronic degrees of freedom. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of the canonical CDW compound $2H$-TaSe$_2$ complemented by angle-resolved photoemission spectroscopy. Our results rule out the central-peak scenario for the CDW transition in $2H$-TaSe$_2$ and provide evidence for a novel precursor phase above the CDW transition temperature $T_{CDW}$. The phase at temperatures between $T^{*}\,(= 128.7\,,\rm{K})$ and $T_{CDW}\,(= 121.3\,\rm{K})$ is characterized by a fully softened phonon mode and medium-range ordered ($\xi_{corr} = 100\,\rm{\mathring{A}}- 200\,\rm{\mathring{A}})$ static CDW domains. Only $T_{CDW}$ is detectable in our photoemission experiments. Thus, $2H$-TaSe$_2$ exhibits structural before electronic static order and emphasizes the important lattice contribution to CDW transitions.

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Xingchen Shen, Rolf Heid, Roland Hott, Björn Salzmann, Marli dos Reis Cantarino, Claude Monney, Ayman H. Said, Bridget Murphy, Kai Rossnagel, Stephan Rosenkranz, Frank Weber. 2022-07-22. Precursor phase with full phonon softening above the charge-density-wave phase transition in $2H$-TaSe$_2$. https://doi.org/10.1038/s41467-023-43094-5

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