Many-body calculations for the relaxed (110) surface of GaAs

Quantum Monte Carlo methods are a stochastic approach to directly tackle the manybody problem in solids. They have proven to describe virutually exactly the ground state of correlated bulk systems, like the homogeneous electron gas or solids of C, Ge, Si and GaAs. Especially Variational quantum Monte Carlo calculations using nonlocal ab initio pseudopotentials offer a way to study systematically many-body effects at solid surfaces, safely founded on the variational principle “the lower the energy, the better the wave function”. Here we report on first attempts for the relaxed (110) surface of GaAs, serving as a prototype of semiconductor surfaces. A finite layer geometry is chosen as the boundary condition of the multidimensional stochastic integration scheme. The exact many-body Hamiltonian is cast in a form allowing for rapid evaluation. New parameters in the correlated trial wave function increase the variational freedom necessary to take into account the influence of the surface. Their physical meaning and their statistical significance are discussed in detail.