Abstract
The anisotropic changes in the electronic structure of a metal-to-insulator transition (MIT) material, RuAs, with a two-step phase transition are reported by using polarized optical conductivity spectra, angle-integrated photoelectron (PE) spectra, and band calculations based on the local-density approximation (LDA). Both the PE and spectra, not only in the high-temperature (HT) phase but also in the low-temperature (LT) phase as well as the energy gap formation owing to the MIT, were almost consistent with those derived from the LDA band calculations, so the fundamental electronic structure in the HT and LT phases can be explained without electron correlations. However, the electronic structure in the middle phase between the HT and LT phases has not been clarified. The polarized spectra revealed not only the anisotropic energy gap formation but also the anisotropic gap-opening temperature; that is, the energy gap along the axis in the HT phase starts to open near the higher transition temperature, but that along the axis opens below the lower transition temperature. The finding suggests that the two-step MIT originates from the anisotropic energy gap formation.
- Received 9 August 2019
- Revised 11 September 2019
DOI:https://doi.org/10.1103/PhysRevB.100.125151
©2019 American Physical Society