Dear Sir,
I am a PhD student of Hong Kong University of Science and Technology. I
want to use KWANT to caculate Hall resistance of a Hall bar structure.We
can get the conductance between 6 electrodes, but how to get hall
resistance? Can you give me some help? Thank you very much.
Best Regards,
Zhang Bing

Dear all,
I want to calculate the conductance and the band structure of a bulk
graphene system.(infinite in y direction) I have checked the source code
for the calculation of band structure.
https://github.com/kwantproject/kwant/blob/7c55b0cb2d0dec163e5483dea8ffdbc8…
It seems that we can get the sys.cell_hamiltonian and hopping between the
sys.cell_hamiltonian in kwant. In y direction, we can also have
sys.cell_hamiltonian and hopping, then it can be extended to infinite in y
direction: V^\dagger e^{iky} + H + Ve^{-iky}. I am not familiar with kwant
coding. Can anyone help me to write some code lines to do these
calculations? Or you can also change the Tutorial 2.2.3 as an example.
Thanks in advance!
Best wishes
Weiyuan Tong

Hello Everyone!
There is given a parameter Excitation energy when we calculate scattering
matrix or LDOS. Can anyone please give more details about this parameter.All
I can understand is that it is the energy with which electron travel in
scattering region.
when we calculate LDOS we get the probability with which electron of that
excitation energy can move in crystal.
What is confusing that I have already applied voltage across the device. How
still conductance changes when I change the value of Excitation energy. Is
it calculating conductance for that energy level only or what? Information
about how this value get processed would be helpful.
Thank you

Dear Colleagues,
Imagine, I have two different 2D lattices in a heterostructure and
want to set up interlayer hoppings between the close-by
atoms. I solve this problem in the way presented below. This works,
but to my surprise it works so slowly that it became a bottle-neck of
my whole computation. Is there a way to improve the code below?
(I suspect, it may be the tag comparison that slows down the thing,
but I am not sure)
def connect(sys,crit):
for site1, site2 in it.product(sys.sites(), repeat=2):
if crit(site1, site2):
yield (site1, site2)
def critInterlayer(site1,site2): ## gamma1 hopping integral
diff = site1.pos-site2.pos
[x,y] = diff
if (abs(x)+abs(y)<0.1) and (site1.tag!=site2.tag):
return True
else:
return False
sys[connect(sys,critInterlayer)]=hopping
Best wishes,
Sergey

Dear users,
I am trying to calculate band structure of Quantum dot (simple sqaure
lattice implementation). Since KWANT's bands() function needs infinite
system to calculate band structure. Please share if anyone has a trick to
calculate BS of quantum dot.

Hi,
I want to calculate conductance between two different leads. This is what I have tried:
1. build an empty center area. This does not work because kwant doesn't know how to attach leads to an empty area.
2. use lead_1.attach_lead(lead_2). Kwant.plot does not correctly plot two leads, so I suppose it doesn't work.
I don't want to build a center area that is the same with one of the leads, because my system is very large and I suppose this will be time-consuming.
Best!
Chong Wang
Ph. D. candidate
Institute of Advanced Study, Tsinghua University, Beijing 100084

My question is not really about Kwant, but about how to install Jupyter. I
have a 64-bit operating system with Windows 8. I have successfully
installed Python 3.4. I want to install Jupyter notebook, but I am not sure
what files I need from Cristoph Gohlke's website (
http://www.lfd.uci.edu/~gohlke/pythonlibs/). When I eventually get the
required files, what is the installation procedure? Can any one advise?
Thank you.
-Joe
--
Joseph Kulik

Dear all,
I want to model a random variation of hopping integrals. Simply writing:
def hopping(sitei, sitej):
return -1 + random.gauss(0,0.2)
does not work since this does not ensure that the hopping is
Hermitian. Is there a smart way to write something like:
def hopping(sitei, sitej):
if sitei<sitej:
return -1 + random.gauss(0,0.2)
else: return Conjugate(hopping(sitej,sitei))
?
Thanks and best wishes,
Sergey

Dear all,
maybe mine is a stupid question, but I’m not sure about the units of measure of the velocities of the propagating modes.
I mean, if, e.g., the parameters entering my tight binding system are the lattice constant a, the nearest neighbor hopping
energy and the Fermi level, to get the right dimensions of a velocity I need to introduce the Planck constant somewhere.
Thus, my question is simply which are the units in which kwant gives back the velocities of the propagating modes?
Thank you for your attention!
Best regards,
Michael Beconcini