Hi Lorenzo,

Indeed, you are right; please see for example this tutorial:
https://kwant-project.org/doc/1/tutorial/discretize#limitations-of-discretization

Best,
Anton

On Tue, 18 Jan 2022 at 16:31, Lorenzo BAGNASACCO <lorenzo.bagnasa...@sns.it>
wrote:

> Dear Kwant community,
>
>
> Thanks for the quick reply.
>
> I plot the band structure and I obtaine the figure I attached. For a
> free-particle I expect a band structure like quadratic dispersion (E \sim
> k^2). The plot of structure band is nearly quadraic. Is it due to
> discretization of the system ? So it means that the wave-function sent to
> the left lead (in my example) is not a free-plane-wave ? Is there a way to
> control the wave-function injected in the lead ?
>
> Yours sincerely
>
> Lorenzo Bagnsacco
>
> Il giorno mar 18 gen 2022 alle ore 15:40 Anton Akhmerov <
> anton.akhmerov...@gmail.com> ha scritto:
>
>> Hi Lorenzo,
>>
>> You need to compute the transmission at an energy where the leads have
>> modes. At E = 10 in your system there aren't any.
>>
>> Plotting the band structure of the leads helps. Check out also the Kwant
>> tutorial at https://kwant-project.org/doc/1/tutorial/
>>
>> Best,
>> Anton
>>
>> On Tue, 18 Jan 2022 at 15:37, Lorenzo BAGNASACCO <
>> lorenzo.bagnasa...@sns.it> wrote:
>>
>>> Dear Kwant community,
>>>
>>> I am a physics student and I am approaching to Kwant to solve simple
>>> problems of scattering.
>>> I am new in Kwant and, for this reason, I'm trying to use Kwnat for
>>> basic problems of scattering.
>>> The most simple problem in my mind is the scattering of a plane-wave (1
>>> dimension) from the left of a potential barrier. If we now suppose the
>>> potential barrier is 'zero' everywhere, the scattering matrix, according to
>>> the scattering theory, should be 'S={{0,1},{1,0}}'.
>>> If I try to compute the reflection and transmission coefficient, I
>>> obtained the correct values (1 for reflection and 0 for transmission). But
>>> it occurs only for some energies. For example in the code I attached, if I
>>> put the value of '10' in  'S=kwant.solvers.default.smatrix(syst,10)' I
>>> obtaine for reflection and transmission the value of '0'. Where is my
>>> errors? And, is there a way to print the entire elements of the scattering
>>> matrix ?
>>>
>>> Yours sincerely
>>>
>>> Lorenzo Bagnasacco
>>>
>>>

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