Optical Study of Electronic Structure of Graphite

Abstract

Reflectance spectra of pyrolytic graphite are measured in the range 0.13 to 0.006 eV. The results are analyzed by a Kramers-Kronig relation to determine the complex dielectric constant ε(ω)=ε₁+iε₂ and energy loss function. Structures in ε₂ are all identified with interband transitions between the doubly degenerate levels at the points K and H of the Brillouin zone split by the effect of spin-orbit interaction. From the above fact, the strength of the coupling λ and the band parameter Δ are estimated as 0.004 eV (at the point K) or 0.0023 eV (at the point H) and -0.016 eV, respectively. Two peaks observed in -Im ε⁻¹ are interpreted as plasma frequencies of free electrons at the Fermi surface perpendicular and parallel to the crystallographic c axis.