Monney, Claude Herzog, Marc Pulkkinen, Aki Huang, Y. Pelliciari, Jonathan Olalde-Velasco, P. Katayama, Naoyuk Nohara, Minoru Takagi, Hide Schmitt, Thorsten Mizokawa, Takashi 2020-08-25 The transition metal chalcogenide Ta2NiSe5 undergoes a second-order phase transition at Tc=328K involving a small lattice distortion. Below Tc, 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 Ta2NiSe5 in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ni L3 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. application/pdf https://folia.unifr.ch/global/documents/309012 https://folia.unifr.ch/documents/309012/files/mon_mus.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.102.085148 info:eu-repo/semantics/openAccess License undefined Physical Review B. - 2020, vol. 102, no. 8, p. 085148 info:eu-repo/classification/udc/53 Mapping the unoccupied state dispersions in ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ with resonant inelastic x-ray scattering http://purl.org/coar/resource_type/c_6501