Hello everybody,

I was trying to run a simulation on the one-dimensional superlattice Bose-Hubbarad with alternating tunneling rates t1 and t2, which is the bosonic analogue of the Su-Schrieffer-Heeger(SSH) model. The lattice with one unit cell is made of A and B sites.

To this end, I have adaped the following unit-cell:

<UNITCELL name="sublattice1d" dimension="1">

  <VERTEX type="0"/>
  <VERTEX type="1"/>
  <EDGE type="0"><SOURCE vertex="1" offset="0"/><TARGET vertex="2" offset="0"/></EDGE>
  <EDGE type="1"><SOURCE vertex="2" offset="0"/><TARGET vertex="1" offset="1"/></EDGE>
  <EDGE type="0"><SOURCE vertex="1" offset="1"/><TARGET vertex="2" offset="1"/></EDGE>
</UNITCELL>

This enters into the lattice graph:

<LATTICEGRAPH name = "2 band sublattice open chain lattice">

  <FINITELATTICE>
    <LATTICE ref="chain lattice"/>
    <EXTENT dimension="1" size ="L"/>
    <BOUNDARY type="open"/>
  </FINITELATTICE>
  <UNITCELL ref="sublattice1d"/>
</LATTICEGRAPH>

And the Hamiltonian:

<HAMILTONIAN name="boson Hubbard">
  <PARAMETER name="mu" default="0"/>
  <PARAMETER name="hop" default="1"/>
  <PARAMETER name="hop'" default="1"/>
  <PARAMETER name="U" default="0"/>
  <BASIS ref="boson"/>
  <SITETERM site="i">
    <PARAMETER name="mu#" default="mu"/>
    <PARAMETER name="U#" default="U"/>
    -mu#*n(i)+U#*n(i)*(n(i)-1)/2
  </SITETERM>  
   <BONDTERM type="0" source="i" target="j">
     -hop*boson_hop(i,j)
   </BONDTERM>
   <BONDTERM type="1" source="i" target="j">
     -hop'*boson_hop(i,j)
   </BONDTERM>
</HAMILTONIAN>

However when I run a DMRG calculation.I still get the wrong results.I compare the ground state energy of it with which I calculated by matlab using ED method.All the parameters of the two calculation are the same.

I seem to misunderstand the implementation. So the question I want to ask is that are there any wrong in the definitions of my lattice or the model in XML.

Thank you for any kind of heplful remarks.

Yulian Chen