Electronic structure of semiconductor nanoparticles from stochastic evaluation of imaginary-time path integral: nonrelativistic U(1) lattice gauge theory in the Kohn-Sham basis

In the Kohn-Sham orbital basis imaginary-time path integral for electrons in a semiconductor nanoparticle has a mild fermion sign problem and is, therefore, amenable to evaluation by the standard stochastic methods. Utilizing output from the density functional theory simulations we compute imaginary-time electron propagators in several silicon hydrogen-passivated nanocrystals, such as Si₃₅H₃₆, Si₈₇H₇₆ and Si₁₄₇H₁₀₀, and extract energies of low-lying electron and hole levels. Our qasiparticle gap predictions are in very good agreement with the results of recent G₀W₀ calculations.