Correlated adatom trimer on metal surface: A continuous time quantum   Monte Carlo study
  The problem of three interacting Kondo impurities is solved within a numerically exact continuous time quantum Monte Carlo scheme. A suppression of the Kondo resonance by interatomic exchange interactions for different cluster geometries is investigated. It is shown that a drastic difference between the Heisenberg and Ising cases appears for antiferromagnetically coupled adatoms. The effects of magnetic frustrations in the adatom trimer are investigated, and possible connections with available experimental data are discussed. 
V.V. Savkin, A.N. Rubtsov, M.I. Katsnelson, A.I. Lichtenstein