Electronic structure and resonant inelastic x-ray scattering in Ta2NiSe5

TL;DR

This study explores the electronic structure of Ta2NiSe5 using resonant inelastic x-ray scattering and density-functional theory, revealing insights into its semiconducting properties and spectral features related to charge transfer excitations.

Contribution

It combines experimental RIXS measurements with advanced DFT calculations, including self-interaction corrections, to analyze the electronic structure and spectra of Ta2NiSe5.

Findings

RIXS spectra show charge transfer excitations involving ligand-to-metal transitions.

DFT with SIC reproduces the semiconducting ground state of Ta2NiSe5.

Spectral analysis reveals the electronic transitions at Ta and Ni L3 edges.

Abstract

We study the electronic structure of Ta2NiSe5 in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ta L3 edge. We also investigate the electronic properties of Ta2NiSe5 within the density-functional theory using the generalized gradient approximation in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. While ARPES, dc transport, and optical measurements indicate that Ta2NiSe5 is a small band-gap semiconductor, DFT gives a metallic nonmagnetic solution in Ta2NiSe5 . To obtain the semiconducting ground state in Ta2 NiSe5 we use a self-interaction correction (SIC) procedure by introducing an orbital-dependent potential Vl into the Hamiltonian. We investigate theoretically the x-ray absorption spectroscopy (XAS) and RIXS spectra at the Ni and Ta L3 edges and analyze the spectra in terms of interband transitions. We investigate the RIXS spectra as a function of momentum transfer vector Q and incident photon energy. Because Ta2 NiSe5 possesses only fully occupied (Ni 3d and Se 4p) and completely empty (Ta 5d) shells with the formal valencies Ta5+ (5d0), Ni0 (3d10 ), and Se2- (4p6 ), both the Ni and Ta L3 RIXS spectra belong to a charge transfer type with ligand-to-metal excitations.