New subject: parameter t' does not seem to work

22 Oct 2018


      Hello Rongyang,
Thank you again.  With your help, I have checked the graph generated from
my lattice definition and corrected my Lattice XML File. But I have a
follow-up question that the tunneling rate t' of the second type bond term
does not work.
I can run the simulation without any bug indicated. Then I found the ground
energy is the same as when I used the "open chain lattice" with a single
tunneling rates t. Next, I deleted the t' in my Parameter XML File. I ran
the calculation again and the ground energy I got was still the same.
I have read the tutorials on ALPS WIKI about the definition of the models.
It is said that 'If the lattice contains more than one site per unit-cell,
the <BASIS> command should contain one <SITEBASIS> entry for each site of
the unit-cell. Each entry should have a different Type, corresponding to
the definitions given in the lattice library file.' (
http://alps.comp-phys.org/mediawiki/index.php/Tutorials:ModelHOWTO)
There is only one type of <SITEBASIS> in my Model XML File. Is this the
source of the problem?
-----------------------Model XML File--------------------------
<MODELS>
<SITEBASIS name="boson">
  <PARAMETER name="Nmax" default="infinity"/>
  <QUANTUMNUMBER name="N" min="0" max="Nmax"/>
  <OPERATOR name="bdag" matrixelement="sqrt(N+1)">
    <CHANGE quantumnumber="N" change="1"/>
  </OPERATOR>
  <OPERATOR name="b" matrixelement="sqrt(N)">
    <CHANGE quantumnumber="N" change="-1"/>
  </OPERATOR>
  <OPERATOR name="n" matrixelement="N"/>
</SITEBASIS>
<BASIS name="boson">
  <SITEBASIS ref="boson"/>
  <CONSTRAINT quantumnumber="N" value="N_total/2"/>
</BASIS>
<SITEOPERATOR name="double_occupancy" site="x">
  n(x)*(n(x)-1)/2
</SITEOPERATOR>
<BONDOPERATOR name="boson_hop" source="x" target="y">
  bdag(x)*b(y)+bdag(y)*b(x)
</BONDOPERATOR>
<HAMILTONIAN name="boson Hubbard">
  <PARAMETER name="mu" default="0"/>
  <PARAMETER name="t" default="1"/>
  <PARAMETER name="t'" default="1"/>
  <PARAMETER name="U" default="0"/>
  <PARAMETER name="V" 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">
     -t*boson_hop(i,j)
   </BONDTERM>
   <BONDTERM type="1" source="i" target="j">
     -t'*boson_hop(i,j)
   </BONDTERM>
</HAMILTONIAN>
</MODELS>
---------------------END-----------------------------
Is there anything wrong with my Model XML File? How can I solve this
problem?
Best,
Yulian

Re: [ALPS-users] parameter t' does not seem to work