I hope you are doing great. We met at the DPG meeting this year (I recognized you in a talk, went to yours, and asked you about time evolution for open systems).

I am writing now because I am trying to implement an iDMRG code on a ladder system. My code is huge, but I'll try to point out the most important parts related to my questions.

The system I am studying is the Fermi-Hubbard model over a squared ladder, and I am now trying to reproduce the results in Fig. 2 (a) at https://doi.org/10.1103/PhysRevB.102.035163. For that, I am using a unit cell of size 2X16.

I am adding the hoppings manually in the form (assume I did it correctly with the spins and H.c terms):

Code: Select all

```
self.add_local_term(-t, [('Cdu', (0, 0))), ('Cu', (1, 0))])
self.add_local_term(-tv, [('Cdu', (0, 0))), ('Cu', (0, 1))])
self.add_local_term(-t, [('Cdu', (0, 1))), ('Cu', (1, 1))])
```

I am setting the lattice with:

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`lat = Ladder(L, site, bc='periodic', bc_MPS='infinite')`

I manually added the hoppings for periodic boundary conditions with add_local_terms; was I supposed to do so, or is it necessary to use add_coupling and

` self.lat.nearest_neighbors`

so that the code captures these boundary conditions?Thanks a lot in advance,

F. P. M. Méndez-Córdoba.