The Haldane phase of spin-1 Heisenberg chain belongs to symmetry protected topological phase. In PhysRevB.81.064439 and many other works it is said that the entanglement spectrum has two-fold degeneracy and it correspond to gapless edge modes. In this work they use iTEBD method. I suppose finite-size DMRG method will also get the double degeneracy of entanglement spectrum if the system is long enough.

In fact in the ITensor calculation of spin-1 chain, I get an entanglement spectrum like

0.48469

0.48469

0.00741

0.00741

0.00741

0.00741

4.00531E-4

4.00531E-4

3.32937E-5

3.32937E-5

3.32937E-5

3.32937E-5

They are almost double degenerate. But their value are not same as the iTEBD result in PhysRevB.81.064439. I just wonder if this method is efficient to detect entanglement spectrum and topological properties in general. Thank you very much!