Absence of topological degeneracy in the Hubbard model on honeycomb lattice
Department of Physics, Renmin University of China - Beijing 100872, PRC
Accepted: 19 January 2011
It is shown that the unique sign structure of the ground state of the Hubbard model on honeycomb lattice, which is shown to be insensitive to the trapped Z2 gauge flux when the system is defined on a torus, may cause the absence of topological degeneracy on this bipartite system. Examples of variational Mott insulating state on the honeycomb lattice are given to illustrate the close relation between the sign structure of the ground state and the (absence of) topological degeneracy.
PACS: 75.10.Kt – Quantum spin liquids, valence bond phases and related phenomena / 71.27.+a – Strongly correlated electron systems; heavy fermions
© EPLA, 2011