Raman Spectra and Excitonic Effects of the novel Ta$_2$Ni$_3$Te$_5$ Monolayer

TL;DR

This study explores the vibrational and optical properties of the novel 2D Ta$_2$Ni$_3$Te$_5$ monolayer, revealing its stability, excitonic effects, and potential for experimental synthesis.

Contribution

It provides the first detailed analysis of the Raman spectra, excitonic effects, and optical anisotropy of Ta$_2$Ni$_3$Te$_5$ monolayer, including vibrational mode identification and stability assessment.

Findings

Monolayer is an indirect band gap semiconductor with gaps of 0.09 eV and 0.38 eV.

Identified ten Raman and ten infrared active vibrational modes.

Exhibits a high exciton binding energy of 287 meV and strong ultraviolet reflectivity.

Abstract

We have investigated the Raman spectrum and excitonic effects of the novel two-dimensional Ta$_2$Ni$_3$Te$_5$ structure. The monolayer is an indirect band gap semiconductor with an electronic band gap value of 0.09 eV and 0.38 eV, determined using GGA-PBE and HSE06 exchange-correlation functionals, respectively. Since this structure is energetically, dynamically, and mechanically stable, it could be synthesized as a free-standing material. We identify ten Raman and ten infrared active modes for various laser energies, including those commonly used in Raman spectroscopy experiments. It was also observed that the contribution of Ni atoms is minimal in most Raman vibrational modes. In contrast, most infrared vibrational modes do not involve the vibration of the Ta atoms. As far as the optical properties are concerned, this monolayer shows a robust linear anisotropy, an exciton binding energy of 287 meV, and also presents a high reflectivity in the ultraviolet region, which is more intense for linear light polarization along the x-direction.