Thank you  very much for your prompt reply.

I do not have any problem with the energies below -2t
but I am wondering why we have current for E=0.
My guess is  the current should be zero at E=0 instead of E= -2t.


On Wed, Aug 26, 2015 at 3:13 PM, Anton Akhmerov <anton.akhmerov@gmail.com> wrote:
Hi Bahareh,

That's quite simple: at the energy below -2t you have no propagating
modes in the wire and in the leads that you attach, and therefore
there's no conduction. So it's nothing really to fix, that is how your
system behaves.


On Wed, Aug 26, 2015 at 2:49 PM, Bahareh Goldozian
<bahareh.goldozian@teorfys.lu.se> wrote:
> Hello,
> I have tried to find the conductance for a three dimensional nanowire,
> I got some current for the zero energy however the current goes to zero when
> the energy is "-2t"
> How can I fix this problem?
> Thank you!
> Bahareh