• DOI:10.1103/physrevb.102.085148
• Corpus ID: 221006432

Mapping the unoccupied state dispersions in Ta2NiSe5 with resonant inelastic x-ray scattering

@article{Monney2020MappingTU,
  title={Mapping the unoccupied state dispersions in 
Ta2NiSe5
 with resonant inelastic x-ray scattering},
  author={Claude Monney and Marc Herzog and Aki Pulkkinen and Y B Huang and Jonathan Pelliciari and Paul Olalde-Velasco and Naoyuki Katayama and Minoru Nohara and H. Takagi and Thorsten Schmitt and Takashi Mizokawa},
  journal={Physical Review B},
  year={2020},
  volume={102},
  pages={085148}
}

• C. Monney, M. Herzog, +8 authors T. Mizokawa
• Published 6 August 2020
• Physics
• Physical Review B

The transition metal chalcogenide ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ undergoes a second-order phase transition at ${T}_{c}=328\phantom{\rule{0.16em}{0ex}}\text{K}$ involving a small lattice distortion. Below ${T}_{c}$, a band gap at the center of its Brillouin zone increases up to about 0.35 eV. In this work, we study the electronic structure of ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ni ${L}_{3}$ edge. In addition to a weak fluorescence response, we observe a collection of intense Raman-like peaks that we attribute to electron-hole excitations. Using density functional theory calculations of its electronic band structure, we identify the main Raman-like peaks as interband transitions between valence and conduction bands. By performing angle-dependent RIXS measurements, we uncover the dispersion of these electron-hole excitations that allows us to extract the low-energy boundary of the electron-hole continuum. From the dispersion of the valence band measured by angle-resolved photoemission spectroscopy, we derive the effective mass of the lowest unoccupied conduction band.