Dear Anton,
I note that when there is a magnetic field in the lead, the momenta depends on 
the position of the lead. Is my observation correct? I guess it is related to 
the algorithm used in finding the momenta of the modes with a fixed energy. Am 
I right?
With regards,
KS Chan

On 12/3/2017, 11:47 PM, "[email protected] on behalf of Anton Akhmerov" 
<[email protected] on behalf of [email protected]> wrote:

    Dear KS Chan,

    The lead momenta, just like lead velocities are the lattice momenta
    and have in general no relation with the coordinate system. The wave
    function is proportional to the exp(i k n), with n the number of the
    lead unit cell and k the momentum.

    I hope that helps,
    Anton

    On Thu, Mar 9, 2017 at 8:53 AM, Prof. CHAN Kwok Sum
    <[email protected]> wrote:
    > Dear Kwant developer,
    >
    > Thank you for your effort in developing Kwant.
    >
    > I have a question about the definition of the direction of momentum in the
    > smatrix.lead_info. Assume a lead lies along the y direction with primitive
    > vector (0,1).  The symmetry operation of  a lead is (0,1) if the lead goes
    > towards the positive direction and is  (0,-1) if the lead goes towards the
    > negative direction. For the momenta contained in smatrix.lead_info for 
these
    > two leads , do they use the same coordinate system? Positive momenta mean
    > the direction (0,1), negative momenta mean the direction (0,-1). For
    > velocity, in smatrix.lead_info, it has nothing to do with the coordinate
    > system. Positive means outgoing, negative means incoming in the lead.
    >
    > Thank you
    >
    > KS Chan
    >
    >
    >
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