Energy gap for Odd and Even length
Posted: 11 Mar 2021, 09:12
Hi,
In the case of the Bose-Hubbard chain, while I calculated charged energy gap (\(\Delta_c=E_0(N+1)+E_0(N-1)-2E_0(N)\)) for L=even, I found the density waves regime as gapped. However, if we do the same calculation with L=odd ( the same even length+1), I found the energy gap as 0, sometimes negative. Although I am not sure but is this problem related to the way it is programmed? As the truncation error is good enough and it converges (norm_error), I don't think it is related to bond-dimensions.
In the case of the Bose-Hubbard chain, while I calculated charged energy gap (\(\Delta_c=E_0(N+1)+E_0(N-1)-2E_0(N)\)) for L=even, I found the density waves regime as gapped. However, if we do the same calculation with L=odd ( the same even length+1), I found the energy gap as 0, sometimes negative. Although I am not sure but is this problem related to the way it is programmed? As the truncation error is good enough and it converges (norm_error), I don't think it is related to bond-dimensions.