Quasiparticle surface band structure and photoelectric threshold of Ge(111)-2×1

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Abstract
The surface-state energies of the Ge(111)-2×1 surface are calculated using a quasiparticle self-energy approach. The surface structural parameters are determined through a local-density-functional total-energy minimization resulting in a buckled π-bonded-chain geometry. The quasiparticle energies are computed using a first-order expansion of the electron self-energy operator in the screened Coulomb interaction with a model static dielectric matrix. Our calculated surface-state band gaps and dispersions of both the occupied and unoccupied surface states agree well with experiments. Further, the photoelectric threshold φ is found to be 4.73 eV, compared to 4.74–4.80 eV obtained experimentally.