Local versus nonlocal correlation effects in interacting quantum spin Hall insulators

The impact of Coulomb interaction on the electronic properties of a quantum spin Hall insulator is studied using quantum cluster methods, disentangling local from nonlocal effects. We identify different regimes, according to the value of the bare mass term, characterized by drastically different self-energy contributions. For small mass, nonlocal correlations start to be important and eventually dominate over local ones when getting close enough to the zero-mass semimetallic line. For intermediate and large mass, local correlation effects outweigh nonlocal corrections, leading to a first-order topological phase transition, in agreement with previous predictions.