## The EE is different for different initial setup

How do I use this algorithm? What does that parameter do?
yhang
Posts: 3
Joined: 15 Jul 2022, 18:58

### The EE is different for different initial setup

Hi, all, I am trying to implement a heisenberg chain with alternating bond strength. I am implementing using XXZ model from tenpy. However, when I try to calculate the entanglement entropy(EE), the result is different for different initial setup. Any suggestions here? Thank you so much! Here is my code for setup, basically if I change the setup of my last line shown here, the entanglement entropy will change, which I don't think it should be like this

Del=2.0
L=200
f=open("ssh_interaction_odd_Jz_2_even_L_200_spin_2.txt","w")
for delta in deltas:
print(delta)
N=L*2
J=np.array([1+delta if i%2==0 else 1-delta for i in range(N-1)])
Jz=np.array([(1+delta)*Del if i%2==0 else (1-delta)*Del for i in range(N-1)])
model_params = {
'L': N,
'Jxx': J,
'Jz':Jz,
'hz':0, # just free fermions, but you can generalize...
'bc_MPS':'finite'
}
M = XXZChain(model_params)
product_state = ['up', 'down']*(L-1)+["up","up"]
Johannes
Try to play with a) different initial states which are in the same charge sector, and b) conserve=None in the model.