Electronic structure and resonant inelastic x-ray scattering in Ta2NiSe5

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 (DFT) 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 Ta2NiSe5 we use a self-interaction-like correction procedure by introducing an orbital-dependent potential Vl into the Hamiltonian. We investigate theoretically the x-ray absorption spectroscopy and RIXS spectra at the Ni and Ta L3 edges and analyze the spectra in terms of interband transitions. We also investigate the RIXS spectra as a function of momentum transfer vector Q and incident photon energy.