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 am using Kwant to study a system with both spins and electron and hole,
so the hopping matrix is 4X4. Now I want to know how to separate the spins,
electron and hole. I study this through the "2.6. Superconductors: orbital
degrees of freedom, conservation laws and symmetries"
smatrix = kwant.smatrix(syst, energy)
data.append(smatrix.submatrix((0, 0), (0, 0)).shape[0]
-smatrix.transmission((0, 0), (0, 0)) +smatrix.transmission((0, 1), (0, 0)))
I do not find more information about this for kwant.
For my system, if I have 3 leads, and the hopping and onsite energy is set
in this order:
(e↑,0,0,0)- spin up electron,first row of the 4X4matrix
(0,e↓,0,0)- spin down electron,second row of the 4X4matrix
(0,0, h↑ ,0)- spin up hole,third row of the 4X4matrix
(0,0, 0, h ↓ )- spin down hole,fourth row of the 4X4matrix
I want to obtain the transmissions from 0 →2.
smatrix = kwant.smatrix(syst, energy)
The transmission from h↑ to e↑ is: smatrix.transmission((2, 1), (0, 2))
The transmission from h ↓ to e↑ is: smatrix.transmission((2, 1), (0, 3))
Is my understanding correct?
Thanks very much in advance!
Hosein Khani
Dear everyone,
I would like to study gas dynamics and absorption within a transition-metal based crystal.
Is possible to realize a simplified Kubas bonding model in tight binding through a simple s-d interaction?
Could I distinguish physisorption by chemisorption by Kubas adsorption at this level of theory?
Any comment or suggestion would be highly appreciated.
Thank you
-----------------------------
Marco Di Gennaro
Toyota Motor Europe
-----------------------------
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Dear all,
is it implemented a way to calculate the density or the density of states
of a lead (defined as kwant.TranslationalSymmetry ...)?
Thank you.
Regards,
Jacopo
Dear Sudin,
Your code seems to work fine for me.
Why don't you just use an onsite function as below? (you can put a
condition as you wish)
sys_2[site] returns a function so you need to add the argument of hat
function: sys_2[site](site)
(be careful, this will not work if the leads add some sites to the central
system: in the lead, the potential is given by scalars, in the system by a
function. a small modification is required)
I hope this helps,
Adel
#############################################################################
def make_system(W, L, lim):
## scattering region ##
def Onsite(site):
x,y=site.pos
if y< lim: return x
else: return 0
sys = kwant.Builder()
sys[lat.shape(cross(W,L), (0,0))] = Onsite
sys[lat.neighbors(1)] = -1.
leads = [create_lead_h(W, xsym1,axis=(0,0)),create_lead_h(W,
xsym2,axis=(0,0))]
for lead in leads:
sys.attach_lead(lead)
return sys
def main():
sys_2 = make_system(W=3.5, L=3, lim=-1)
kwant.plotter.plot(sys_2,site_color=lambda
site:sys_2[site](site),colorbar=True, cmap=None)
if __name__ == '__main__':
main()
On Fri, Apr 17, 2020 at 7:06 AM SUDIN GANGULY <sudinganguly(a)gmail.com>
wrote:
> Dear Sir,
>
> Thank you for your reply. The problem I am facing is that if I assign the
> site values like (1,2,3,...) along the bottom line, the colormap of the
> site values are changing whenever I compile the code.
> ############################
> import kwant
> from pylab import *
> import matplotlib.pyplot as plt
> from random import *
> import numpy as np
>
>
> class Honeycomb(kwant.lattice.Polyatomic):
> def __init__(self, name=''):
> prim_vecs = [[0.5, sqrt(3)/2], [1, 0]] # bravais lattice vectors
> # offset the lattice so that it is symmetric around x and y axes
> basis_vecs = [[-0.5, -1/sqrt(12)], [-0.5, 1/sqrt(12)]]
> super(Honeycomb, self).__init__(prim_vecs, basis_vecs, name)
> self.a, self.b = self.sublattices
>
> sys=kwant.Builder()
> lat = Honeycomb()
> a,b= lat.sublattices
>
>
> def cross(W, L):
> def shape(pos):
> return ((-W <= pos[1] <= W and -L <= pos[0] <= L))
> return shape
>
> pv1, pv2 = lat.prim_vecs
>
>
> xsym1 = kwant.TranslationalSymmetry((-pv2)) # lattice symmetry in -x
> direction
> xsym1.add_site_family(lat.sublattices[0], other_vectors=[(-2, 1)])
> xsym1.add_site_family(lat.sublattices[1], other_vectors=[(-2, 1)])
>
> xsym2=kwant.TranslationalSymmetry((pv2))
> xsym2.add_site_family(lat.sublattices[0], other_vectors=[(-2, 1)])
> xsym2.add_site_family(lat.sublattices[1], other_vectors=[(-2, 1)])
>
> def create_lead_h(W, symmetry, axis):
> lead = kwant.Builder(symmetry)
> lead[lat.wire(axis, W)] = 0.
> lead[lat.neighbors(1)] = -1.
> return lead
>
>
> def make_system(W, L, no_of_line):
>
> ## scattering region ##
> sys = kwant.Builder()
> sys[lat.shape(cross(W,L), (0,0))] = 0
> sys[lat.neighbors(1)] = -1.
>
>
> line=[]
> for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
> line.append(site.pos[1])
>
>
> line=set(line)
> line=list(line)
> line=sort(line)
> my_list=[]
> i=1
> for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
> for j in range(0,no_of_line+1,2):
> line_no=j
> if (site.pos[1]==line[line_no] or
> site.pos[1]==line[line_no+1]):
> my_list.append(site)
> sys[site]=i
> i=i+1
>
> ## leads ##
>
> leads = [create_lead_h(W, xsym1,axis=(0,0))]
> leads += [create_lead_h(W, xsym2,axis=(0,0))]
>
> for lead in leads:
> sys.attach_lead(lead)
>
>
> #=============================================================================
> return {'sys': sys }
>
> def main():
> sys_2 = make_system(W=3.5, L=5, no_of_line=1)
> kwant.plotter.plot(sys_2['sys'],site_color=lambda
> site:sys_2['sys'][site],colorbar=True, cmap=None)
>
> if __name__ == '__main__':
> main()
> #################################
>
> I can resolve this issue by collecting the site positions from the array
> named my_list in the given code and then assign the site values
> accordingly. However, this procedure is a bit lengthy. If there is any
> other way to do that with less coding, that will be very helpful.
> With Regards,
> Sudin
>
> On Fri, Apr 17, 2020 at 1:36 AM Abbout Adel <abbout.adel(a)gmail.com> wrote:
>
>> Dear Sudin,
>>
>> Please post the code giving the error or explain better your concern.
>>
>> Could you just do it by defining an on site function?
>>
>> def Onsite(site):
>> x,y=site.pos()
>> i,_=site.tag
>> if y=y0: return Values[i]
>> else: return V0
>>
>>
>> sys[(........)]=Onsite
>>
>> I hope this helps,
>> Adel
>>
>> On Wed, Apr 15, 2020 at 3:45 PM SUDIN GANGULY <sudinganguly(a)gmail.com>
>> wrote:
>>
>>> Dear Sir,
>>>
>>> I want to assign a particular sequence of site values on a particular
>>> line (a number of lines) of a zigzag graphene nanoribbon. For example, the
>>> bottom zigzag line.
>>>
>>> let's say, from the left to right there are 10 sites and I want to put
>>> the onsite values as [1,2,3,...].
>>>
>>> I was able to get the information about the sites that are in the bottom
>>> line and have assigned the site values accordingly. But the problem is that
>>> each time I finalize the system, I get different onsite values along the
>>> bottom line. Is there any way to resolve this? Or maybe this approach is
>>> not the right way to do that.
>>>
>>> A part of my code is given below
>>> ========================
>>> def make_system(W, L, no_of_line):
>>>
>>> ## scattering region ##
>>> sys = kwant.Builder()
>>> sys[lat.shape(cross(W,L), (0,0))] = 0
>>> sys[lat.neighbors(1)] = -1.
>>> #######INFO of the line#########
>>> line=[]
>>> for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
>>> #print (site.pos[0],site.pos[1])
>>> line.append(site.pos[1])
>>>
>>> line=set(line)
>>> line=list(line)
>>> line=sort(line)
>>>
>>>
>>> i=1
>>> for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
>>> for j in range(0,no_of_line+1,2):
>>> line_no=j
>>> if (site.pos[1]==line[line_no] or site.pos[1]==line[line_no+1]):
>>> sys[site]=i
>>> i=i+1
>>> ########################
>>>
>>> With Regards,
>>> Sudin
>>>
>>
>>
>> --
>> Abbout Adel
>>
>
>
> --
> সুদিন
>
--
Abbout Adel
Dear Sir,
I want to assign a particular sequence of site values on a particular line
(a number of lines) of a zigzag graphene nanoribbon. For example, the
bottom zigzag line.
let's say, from the left to right there are 10 sites and I want to put the
onsite values as [1,2,3,...].
I was able to get the information about the sites that are in the bottom
line and have assigned the site values accordingly. But the problem is that
each time I finalize the system, I get different onsite values along the
bottom line. Is there any way to resolve this? Or maybe this approach is
not the right way to do that.
A part of my code is given below
========================
def make_system(W, L, no_of_line):
## scattering region ##
sys = kwant.Builder()
sys[lat.shape(cross(W,L), (0,0))] = 0
sys[lat.neighbors(1)] = -1.
#######INFO of the line#########
line=[]
for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
#print (site.pos[0],site.pos[1])
line.append(site.pos[1])
line=set(line)
line=list(line)
line=sort(line)
i=1
for site in sys.expand(lat.shape(cross(W,L), (0, 0))):
for j in range(0,no_of_line+1,2):
line_no=j
if (site.pos[1]==line[line_no] or site.pos[1]==line[line_no+1]):
sys[site]=i
i=i+1
########################
With Regards,
Sudin
