I'm having issues with iDRMG convergence, and was hoping someone might have an idea of what the issue is.
I'm modeling the following 1D Rydberg Chain Hamiltonian:
H = \(\Sigma [ \Omega (b_j + b_j^+) + V_1 n_j n_{j+1} - \Delta n_j]\)
with the following representations for operators in the Pauli basis:
\(X_j = b_j + b_j^+\)
\(Z_j = 2n_j-1\)
In the blockade regime with \(V_1 = 100\), the system is critical at \(\Delta = 0.664, \Omega = 1.\)
I was able to run finite DMRG with PBC at this point and it converges with the state exhibiting expected power law scaling in its connected correlators. I was able to recover both the Z_2 phase and disordered phase in infinite DMRG, as well. However, when tuning the Hamiltonian to the critical point in infinite DMRG (unit cell size = 2), I experience convergence issues. The energy fluctuates significantly even after a large number of sweeps. I've tried turning the mixer on and off, different chi_lists/chi_max, increasing the number of sweeps, and a few other tests but to no avail.
I was thinking the issue might be the large value of \(V_1\) compared to the other parameters in my Hamiltonian, but I don't see why this issue wouldn't also arise when doing finite DMRG. Any thoughts on what may be the issue, here? Any insight would be much appreciated.