Anisotropy of the g Factor of the Free Hole in Ge and Conduction-Band Spin-Orbit Splitting

We report a significant anisotropy of the g factor of the free hole in uniaxially stressed Ge which represents the first observation in any band structure of the q term postulated by Luttinger in the valence-band Hamiltonian. It is shown that this effect arises from the spin-orbit splitting Δ(Γ₁₅^_^-) of the nearby Γ₁₅^_^- conduction band. The measurements yield the value Δ(Γ₁₅^_^-)=0.15±0.03 eV.