## The problem of Computing momentum entanglement spectrum in infinite dmrg

How do I use this algorithm? What does that parameter do?
kevln
Posts: 2
Joined: 12 May 2022, 07:02

### The problem of Computing momentum entanglement spectrum in infinite dmrg

Hello, this is the first time to use Tenpy, it is quite good and has so many features.

For the last few day I have been trying to calculate the momentum entanglement spectrum in arXiv:1407.6985 with Tenpy. I want to get Fig3.b without considering charge.

In fact, using tenpy/example/chern insulators/haldan.py as an example, I tried some calculations. My naive idea is,
• Change the filling factor to 1/3
• $$\phi_{y}=2\pi$$
• using compute_k()
• change model_params
The corresponding code is

Code: Select all

    prod_state = ['full']
if 2 * model_params['Lx'] * model_params['Ly'] % 3 != 0:
warnings.warn("Total filling factor = 1/3 cannot be achieved with this unit cell geometry.")
for i in range(1, 2 * model_params['Lx'] * model_params['Ly']):
if i % 3 == 0:
prod_state.append('full')
else:
prod_state.append('empty')
print(prod_state)


Code: Select all

    model_params['phi_ext'] = 1


Code: Select all

    print("Computing momentum...")
psi.canonical_form()
u, w, q, o, t = psi.compute_K(M.lat,swap_op='auto')

print('compute_k: ov = ', o)
k = np.angle(w)/np.pi
p = -np.log(np.abs(w))

data['ent_spectrum'].append(p)
data['momentum'].append(k)


Code: Select all

    t1_value = -1
phi = np.arccos(3 * np.sqrt(3 / 43))
t2_value = (np.sqrt(129) / 36) * t1_value * np.exp(1j * phi)  # optimal band flatness

model_params = dict(conserve='N',
t1=t1_value,
t2=t2_value,
mu=0,
V=t1_value,
bc_MPS='infinite',
order='default',
Lx=1,
Ly=6,
bc_y='cylinder',
verbose=0)

Besides these, I didn't make any other changes to tenpy's haldan.py, including some parameters related to dmrg sweep, but my results were terrible,like

in Ly=3,and

in Ly=6
l want to know the reason for this error, any reply and help from you will help me a lot in in using Tenpy!!!Thanks for your help!!!
kevln
Posts: 2
Joined: 12 May 2022, 07:02

### Re: The problem of Computing momentum entanglement spectrum in infinite dmrg

Why my questions can not be seen by others? Is there something wrong with my content?