Figure 1.

Characterizations of the Ta₂NiSe₅ single crystals. a) Atomic structure of the Ta₂NiSe₅ stacked along the b axis. b) Top view of crystallographic structure of the Ta₂NiSe₅. c) XRD pattern of the Ta₂NiSe₅ crystals. Inset shows the optical image of the Ta₂NiSe₅ single crystal. d–f) High‐resolution XPS spectra of Ta 4f, Ni 2p, and Se 3d core regions in the Ta₂NiSe₅ crystal, respectively. g) FTIR absorption spectrum of the mechanically exfoliated Ta₂NiSe₅ nanosheets. h) Raman spectra of the Ta₂NiSe₅ nanoflake with different thickness. i) Band structure of the Ta₂NiSe₅ single crystal measured by ARPES at T = 300 K along the $\overline{\mathrm{\Gamma }}$–$\overline{\mathrm{X}}$ direction.