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arXiv · 1603.03439

Fermionic Symmetry-Protected Topological Phase in a Two-Dimensional Hubbard Model

Cheng-Chien Chen·Lukas Muechler·Roberto Car·Titus Neupert·Joseph Maciejko
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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.

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Cheng-Chien Chen, Lukas Muechler, Roberto Car, Titus Neupert, Joseph Maciejko. 2016-08-25. Fermionic Symmetry-Protected Topological Phase in a Two-Dimensional Hubbard Model. https://doi.org/10.1103/physrevlett.117.096405

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