Dear all,
i used a slightly modified "discretize.py" code of https://kwantproject.org/doc/1/tutorial/discretize%C2%A0 (see attached file)
and added the term
""" + kappa * kron(sigma_z,sigma_0) """
to the hamiltonian (splitting up the different spins). When checking the unitarity of the scattering matrix at energy=0 by applying the function "check_unitarity(matrix)" for
kappa=0 and kappa=10**(9) the unitarityerror is increasing from order 10**(13) to 10**(6) !
Why is the error of $ S^\dagger S$ getting so high?
Thanks in advance!
Andreas Bereczuk
Dear Andreas,
I investigated your code and everything seems correct. I checked your claim, and found it true! For large value kapp=0.0001, the S matrix is unitary. The same for Kappa=0 or kappa <1E13. Around Kappa=1E9, it is not unitary (at least not unitary with the precision set in kwant) I am still puzzled and did not find an answer for that. The only remark I can make is that the edge state at this energy is degenerate and I remember, a case with kwant having a problem happening at the degenerate states.
If it happens that you find the answer, I will be interested to read it.
Best regards, Adel
On Thu, Dec 10, 2020 at 5:49 PM Andreas Bereczuk Bereczuk.A@gmx.de wrote:
Dear all,
i used a slightly modified "discretize.py" code of https://kwantproject.org/doc/1/tutorial/discretize (see attached file)
and added the term
""" + kappa * kron(sigma_z,sigma_0) """
to the hamiltonian (splitting up the different spins). When checking the unitarity of the scattering matrix at energy=0 by applying the function "check_unitarity(matrix)" for
kappa=0 and kappa=10**(9) the unitarityerror is increasing from order 10**(13) to 10**(6) !
Why is the error of $ S^\dagger S$ getting so high?
Thanks in advance!
Andreas Bereczuk
participants (2)

Abbout Adel

Andreas Bereczuk