## Abstract

We study the two-dimensional (2D) Hubbard model using exact diagonalization for spin-1/2 fermions on the triangular and honeycomb lattices decorated with a single hexagon per site. In certain parameter ranges, the Hubbard model maps to a quantum compass model on those lattices. On the triangular lattice, the compass model exhibits collinear stripe antiferromagnetism, implying d-density wave charge order in the original Hubbard model. On the honeycomb lattice, the compass model has a unique, quantum disordered ground state that transforms nontrivially under lattice reflection. The ground state of the Hubbard model on the decorated honeycomb lattice is thus a 2D fermionic symmetry-protected topological phase. This state - protected by time-reversal and reflection symmetries - cannot be connected adiabatically to a free-fermion topological phase.

Original language | English (US) |
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Article number | 096405 |

Journal | Physical review letters |

Volume | 117 |

Issue number | 9 |

DOIs | |

State | Published - Aug 25 2016 |

## All Science Journal Classification (ASJC) codes

- Physics and Astronomy(all)