Chiral bosonic topological insulator on the honeycomb lattice with anisotropic interactions

Amrita Ghosh^1,2*, Eytan Grosfeld²

¹Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
²Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel

* Presenter:Amrita Ghosh, email:amritaghosh@phys.ncts.ntu.edu.tw

Majority of the theoretical models demonstrating a stable topologically ordered phase in two-dimensions (2D), require the presence of exotic terms such as magnetic flux, lattice frustration, etc. We formulate a simple theoretical model of hard-core bosons in 2D which hosts a rich phase diagram consisting of strong as well as weak interacting-topological phases, without the help of any exotic term. We study hard-core bosons on the honeycomb lattice subjected to nearest-neighbor hopping as well as anisotropic nearest-neighbor repulsive interactions. Using a state-of-the-art quantum Monte Carlo (QMC) technique, we extract the phase diagram of the model in terms of the filling and the anisotropy. At half-filling we find a time-reversal-breaking topological insulator phase near maximum anisotropy that is characterized by a finite topological entanglement entropy ln(2)/2, indicative of a fractional quantum Hall state for bosons. We identify the presence of edge states and derive a QMC-based method to extract and verify their chirality. Furthermore, with the introduction of anisotropy in the hopping we find a transition from strong interacting-topological order to weak interacting-topological order. The strong topological phase is characterized by a finite topological entanglement entropy, while the weak topological order is identified with a non-trivial value of the bipartite entanglement entropy.

Keywords: Topological insulator, Bosonic fractional quantum Hall state, Topological entanglement entropy, Interacting-topological order, Quantum Monte Carlo