Dear all,

I am trying to add the spin-orbit coupling term to the 1D Hubbard model. I use the standard files 

for 1D Hubbard model in the library and add those codes: 

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<BONDOPERATOR name="SOC" source="x" target="y">

  cdag_up(y)*c_down(x)-cdag_down(y)*c_up(x)+cdag_down(y)*c_up(x)-cdag_up(y)*c_down(x)

</BONDOPERATOR>

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and 

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  <BONDTERM source="i" target="j">

    <PARAMETER name="t#" default="0"/>

    <PARAMETER name="alpha" default="0"/>

    -t*fermion_hop(i,j)-alpha*SOC(i,j) 

  </BONDTERM>

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to the model XML file just like before. But it seems it does not work. The results keep the same 

when I change the parameter 'alpha' .

Can you give me some advices ? Thank you very much in advance.