Dear Amrita,

Yes, you can add the two builders as follows:
left_lead1+=left_lead2

but in the new version of kwant, the operator += for builders is deprecated. So, you better use:

left_lead1.update(left_lead2)
and then you add your missing hopping, before you attach the lead:
left_lead1[(lat(0,0),lat(0,-1))]=t

I don't know why you separate your lead into two parts and then build it again, but you can get it directly in one shot.

I hope this helps.
Adel

On Fri, Feb 23, 2018 at 10:04 PM, amrita chapagain <amritachapagain@gmail.com> wrote:
Thank  you Adel for prompt reply. I have another query here. Can I add these two system together incorporating missing hopping elements? 



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Abbout Adel