Quantum phases on the triangular lattice: Results for bosons, fermions and antiferromagnets
Prof. Dr. Sebastian Eggert (TU Kaiserslautern)

The antiferromagnetic Heisenberg model on the triangular lattice was proposed as the first example of a spin-liquid by Anderson in the early 70s. Even though the isotropic Heisenberg model is by now well understood and known not to be a spin-liquid in the modern sense, so far the full phase diagram of the xxz model on the triangular lattice has received little attention. We now present detailed numerical and analytical results to establish the full phase diagram as a function of field and exchange coupling J/J_z, which shows rather surprising non-trivial features from the competition of different ordered states. For negative J the system corresponds to hardcore bosons with supersolid behavior. Finally the effect of spin and charge degrees of freedom is considered in the extended Hubbard model on the triangular lattice as a function of filling. In this case, stable charge order can coexists with conducting behavior.