Electronic band structure and anisotropic dielectric response of from angle-resolved photoemission spectroscopy, spectroscopic ellipsometry, and density functional theory: An indirect-gap hyperbolic van der Waals semiconductor
Phys. Rev. B 113, 085407 – Published 4 February, 2026
DOI: https://doi.org/10.1103/glcr-8mqy
Abstract
By combining angle-resolved photoemission, density functional theory, and variable-angle spectroscopic ellipsometry, we determine the bulk electronic structure and anisotropic optical response of platinum disulfide (). Momentum-resolved maps collected at 60 and 85 eV reveal a single holelike branch that peaks at Γ with an effective mass approximately . The measured dispersion along the Γ–M–K direction is reproduced within the experimental resolution by calculations including spin-orbit coupling and recursive Green's function approach in semi-infinite geometry. A photon-energy sweep shows a weak but finite out-of-plane dispersion for the top valence band, establishing its bulk character, while constant-energy maps reveal a ring-shaped extremum approximately 1.5 eV below the valence-band maximum that generates nearly flat segments and a Mexican-hat contour consistent with S-p and Pt-d hybridization and a surface-localized, topologically trivial origin. The same ab initio framework yields an indirect bulk gap of approximately 1.22 eV and a strongly anisotropic dielectric tensor with an in-plane epsilon-near-zero crossing near 3.1 eV. The estimated dielectric tensors indicate the existence of a low-energy anisotropic dielectric region; an intermediate range in which both the real and imaginary parts of the dielectric function are negative and only evanescent, plasmonic modes are supported; and type-I hyperbolic windows where the in-plane and out-of-plane components have opposite signs, including a narrow visible band around 3.14–3.24 eV and a broader range above approximately 3.8 eV. Ellipsometry in the 1.24–3.60 eV range confirms experimentally the same ordering of photonic regimes, with an anisotropic dielectric response at low energy, followed by type-I and type-II intervals, and locates the corresponding zero-crossings at slightly lower photon energies than in theory. These results promote the use of for anisotropic optoelectronic and nanophotonic architectures.
