Putting bosonic complex hopping on Honeycomb lattice check paper (http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.067208 ), the result is not converging and the energy is increasing with each sweep and I am getting the eigenvalues of density matrix greater than one and so negative entanglement entropy. Again when taking real hopping without y-periodicity, for even sweep I am getting zero entanglement entropy, but non-zero for odd sweeps. I have the code if you want I can give you.

Thanks in advance.

You mentioned that you have eigenvalue of density matrix bigger than one. But I think this result must be un-physical, because the eigenvalue is the possibility. Would it be that you didn't normalize the "psi" before building the density matrix?

Zhiyu