Spontaneous quantum Hall effect in quarter-doped Hubbard model on honeycomb lattice and its possible realization in quarter-doped graphene system

TL;DR

This paper demonstrates that quarter-doped Hubbard model on honeycomb lattices exhibits a spontaneous quantum Hall effect with a topologically nontrivial insulating state, potentially realizable in quarter-doped graphene, and relates it to similar phenomena in triangular lattices.

Contribution

It reveals a new topological magnetic insulating state in the quarter-doped Hubbard model on honeycomb lattices, showing its robustness and potential realization in graphene systems.

Findings

Insulating state has quantized Hall conductance of e^2/h.

State is topologically nontrivial with nonzero spin chirality.

Fermi surface nesting persists for arbitrary next-nearest-neighbor hopping.

Abstract

We show that as the result of the nesting property of the Fermi surface, the quarter-doped Hubbard model on honeycomb lattice is unstable with respect to the formation of a magnetic insulating state with nonzero spin chirality for infinitesimally small strength of electron correlation. The insulating state is found to be topological nontrivial and to have a quantized Hall conductance of $\sigma_{xy}=\frac{e^{2}}{h}$. We find the Fermi surface nesting is robust for arbitrary value of next-nearest-neighbor hopping integral. It is thus very possible that the quarter-doped graphene system will realize such an exotic ground state. We also show that the quarter-doped Hubbard model on honeycomb lattice is in exact equivalence in the weak coupling limit with the 3/4-filled Hubbard model on triangular lattice, in which similar effect is also observed.