SrAs3 is a unique nodal-line semimetal that contains only a single nodal ring in the Brillouin zone, uninterrupted by any trivial bands near the Fermi energy. We performed axis-resolved optical reflection measurements on SrAs3 and observed that the optical conductivity exhibits flat absorption up to 129 meV in both the radial and axial directions, confirming the robustness of the universal power-law behavior of the nodal ring. Furthermore, in conjunction with model and first-principles calculations, the axis-resolved optical conductivity unveiled fundamental properties beyond the flat absorption, including the overlap energy of the topological bands, the spin-orbit coupling gap along the nodal ring, and the geometric properties of the nodal ring such as the average ring radius, ring ellipticity, and velocity anisotropy. In addition, our temperature-dependent measurements revealed a spectral weight transfer between intraband and interband transitions, indicating a possible violation of the optical sum rule within the measured energy range.
@article{arxiv.2303.14973,
title = {Optical transitions of a single nodal ring in SrAs$_3$: radially and axially resolved characterization},
author = {Jiwon Jeon and Jiho Jang and Hoil Kim and Taesu Park and DongWook Kim and Soonjae Moon and Jun Sung Kim and Ji Hoon Shim and Hongki Min and Eunjip Choi},
journal= {arXiv preprint arXiv:2303.14973},
year = {2023}
}