Phonon dispersion and electronic structure in quasi-one-dimensional layered Ta2NiSe7 single crystal

Abstract

The formation mechanism of charge density wave (CDW) order in layered systems was believed to arise from momentum-dependent electron–phonon coupling and electronic structure instability induced by Fermi surface nesting. Herein, we systematically investigated the angular dependence of the Raman peak intensity in a ternary layered Ta₂NiSe₇ single crystal through polarized Raman spectroscopy. Combining group theory analysis, the vibrational modes of the Raman peaks were clearly indentified, and the Raman shift was confirmed by our first-principle calculated phonon spectrum. In addition, the electronic band structure near the Fermi level simulated via ab initio density functional theory coincided with angle resolved photoelectron spectroscopy measurements (ARPES). Our study provided a useful foundation for further understanding the CDW transition in layered Ta₂NiSe₇.