Substrate tuning of the structural and electronic transition in thin flakes of the excitonic insulator candidate Ta$_2$NiSe$_5$

Yuan-Shan Zhang; Zichen Yang; Chuanlian Xiao; Masahiko Isobe; Matteo Minola; Hidenori Takagi; Dennis Huang

paper

Substrate tuning of the structural and electronic transition in thin flakes of the excitonic insulator candidate Ta $_{2}$ NiSe $_{5}$

arXiv:2512.12439

Abstract

Ta $_{2}$ NiSe $_{5}$ continues to draw interest for its 326 K phase transition, whose dual electronic and structural nature reflects a complex interplay of electron-hole (excitonic) and electron-lattice interactions. Most studies that have attempted to decipher the relative importance of these interactions, particularly through charge transfer, have been limited to bulk samples. We utilized a thin-flake approach to modify the excitonic interactions in Ta $_{2}$ NiSe $_{5}$ via an underlying film of Au. Using polarized Raman spectroscopy, we found that four layers of Ta $_{2}$ NiSe $_{5}$ supported on conducting Au show a transition temperature that is both reduced by over 100 K and broadened due to an interfacial charge gradient effect, manifesting the presence of excitonic interactions. In contrast, four layers of Ta $_{2}$ NiSe $_{5}$ supported on insulating Al $_{2}$ O $_{3}$ show nearly bulk-like properties. We also report the development of an all-dry exfoliation and transfer protocol that generalizes substrate engineering for strongly correlated van der Waals materials.

24 pages, 5 figures

Substrate tuning of the structural and electronic transition in thin flakes of the excitonic insulator candidate Ta2​NiSe5​

Abstract

Substrate tuning of the structural and electronic transition in thin flakes of the excitonic insulator candidate Ta $_{2}$ NiSe $_{5}$