Gate tuning of coupled electronic and structural phase transition in atomically thin Ta2NiSe5

Keyu Wei; Yixuan Luo; Kenji Watanabe; Takashi Taniguchi; Yanfeng Guo; Xiaoxiang Xi

doi:10.1038/s41467-025-66594-y

論文 Gate tuning of coupled electronic and structural phase transition in atomically thin Ta2NiSe5

Keyu Wei ; Yixuan Luo ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Yanfeng Guo ; Xiaoxiang Xi

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Keyu Wei, Yixuan Luo, Kenji Watanabe, Takashi Taniguchi, Yanfeng Guo, Xiaoxiang Xi. Gate tuning of coupled electronic and structural phase transition in atomically thin Ta2NiSe5. Nature Communications. 2025, 16 (1), 10999. https://doi.org/10.1038/s41467-025-66594-y

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(abstract)

Realizing an excitonic insulator phase from narrow-gap semiconductors remains challenging, as unambiguous experimental signatures are difficult to establish. Ta2NiSe5 has been widely regarded as a leading candidate, yet the nature of its phase transition and insulating state remains controversial. Here, we report a systematic Raman spectroscopy study of Ta2NiSe5 as a function of thickness and field-effect doping, complemented by electrical transport measurements. The phase transition persists down to the monolayer limit, with the critical temperature increasing as thickness decreases. In bilayer samples, both electron and hole doping suppress the insulating state, with electron doping lowering and hole doping raising the critical temperature. Importantly, the quasi-elastic scattering, previously attributed to excitonic fluctuations, evolves monotonically across the entire doping range. These findings suggest that the insulating state arises from a coupled electronic and structural phase transition, with its stability tunable by carrier doping. This doping approach provides a pathway to assess the role of electronic interactions in candidate excitonic insulator materials.

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