Seminar "Coherence-Correlations-Complexity", Dept. of Theoretical Physics, Wrocław University of Technology
Sala 320a bud. A-1, Politechnika Wrocławska
Topological and conventional order in strongly correlated 2D systems from DMRG calculations
dr Johannes Motruk
Max Planck Institute for the Physics of Complex Systems, Dresden
In 2008, Raghu et al. proposed that a system of spinless fermions on the honeycomb lattice can host a topological Chern insulator (CI) phase induced by next-nearest neighbour interactions. This mean field prediction has been challenged by various subsequent studies and the existence of the CI phase has remained a controversial question. In the first part of the talk, I will present our DMRG studies of the model's phase diagram on an infinite cylinder which show the absence of the CI phase, but the presence of two convential charge ordered phases that have not been accounted for in previous studies. Furthermore, we comment on the nature of the transitions between different phases. In the second part, I will turn to fractional Chern insulators (FCI). We show that the FCI state at filling factor 1/3 in the Haldane honeycomb model can be fully characterized within DMRG by computing several quantities that prove its topological order. We additionally demonstrate that the transition between metallic and FCI state at low interaction is of first order. Finally, we show how DMRG calculations on a cylinder can be performed more efficiently by employing a mixed real/momentum space representation.
