Dear KWANT developers,
I want to plot the current density for a 3D model with finite width in x
and y direction. Below is the energy dispersion of the model Hamiltonian.
To calculate the current density profile, I have assumed scattering region
with a width of 60 unit cells in z-direction and leads with different
onsite and same hoppings (as that of scattering region) are attached. For
better understanding the code is attached below. For plotting current
density, I have used 2D slices of y-z plane. Now my question is that, while
building the second system, what onsite and Hopping terms should I have to
use? Because I have already build a 3D system with particular onsite and
hopping terms. Can I use onsite =0 for the second system? and what should
be the hoppings for the second system? can I use simply lat2.neighbors()
for the second system? I tried it in different ways, it gives me different
results. I don't know which one correct. please suggest me the correct
way.
[image: image.png]
*import kwantfrom numpy import exp,sin,linspace,sqrt, cos, piimport
matplotlib as mplfrom matplotlib import pyplot as pltimport tinyarrayimport
pandas as pd*
*sigma_0 = tinyarray.array([[1, 0], [0, 1]])sigma_x = tinyarray.array([[0,
1], [1, 0]])sigma_y = tinyarray.array([[0, -1j], [1j, 0]])sigma_z =
tinyarray.array([[1, 0], [0,
-1]])lat=kwant.lattice.cubic(norbs=2)L=10W=80#H=60def onsite(site):
return (1.0 * cos(1.05) + 2 * 1.0) * sigma_z*
*def onsite_s(site): return (1.0 * cos(1.05) + 2 * 1.0) * sigma_z - 0.75
* sigma_0def hoppingx(site0, site1): return (-0.5 * 1.0 * sigma_z - 0.5
* 1j * 1.0 * sigma_x)def hoppingy(site0, site1): return -0.5 * 1.0 *
sigma_z - 0.5 * 1j * 1.0 * sigma_ydef hoppingz(site0, site1): y =
site1.pos[1] return (-0.5 * 1.0 * sigma_z - 0.5 * 1j * 0.25 * sigma_0) *
exp(-2 * pi * 1j * 0.001 * 1.0 * (y-40))sys=kwant.Builder()sys[(lat(z,y,x)
for z in range(0,10) for y in range(W) for x in
range(L))]=onsite_ssys[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] =
hoppingxsys[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] =
hoppingysys[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] =
hoppingzsys[(lat(z,y,x) for z in range(10,70) for y in range(W) for x in
range(L))]=onsitesys[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] =
hoppingxsys[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] =
hoppingysys[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] =
hoppingzsys[(lat(z,y,x) for z in range(70,80) for y in range(W) for x in
range(L))]=onsite_ssys[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] =
hoppingxsys[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] =
hoppingysys[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] = hoppingz*
*# The scattering region 0 < W_z < 10 and 60 < W_z > 70 have onsite energy
of leads.*
*lead=kwant.Builder(kwant.TranslationalSymmetry((-1,0,0)))lead[(lat(0,y,x)
for y in range(W) for x in range(L))] =
onsite_slead[kwant.builder.HoppingKind((1, 0, 0), lat, lat)] =
hoppingzlead[kwant.builder.HoppingKind((0, 1, 0), lat, lat)] =
hoppingylead[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] =
hoppingxsys.attach_lead(lead)sys.attach_lead(lead.reversed())kwant.plot(sys)sysf=sys.finalized()Sites=list(sysf.sites)#print(Sites)wave=kwant.wave_function(sysf,
energy=0.1)psi=wave(0)[0]#df =
pd.DataFrame(Sites)#df.to_csv('data2.csv',index=False, header=False)def
Plot(x,psi): def cut(site0,site1): return site0.pos[2]==x and
site1.pos[2]==x J_0 = kwant.operator.Current(sysf, where=cut)
current = J_0(psi) lat2=kwant.lattice.square(norbs=2)
sys2=kwant.Builder() sys2[(lat2(site.pos[0],site.pos[1]) for site in
Sites if site.pos[2]==x)]=onsite*
* #sys2[(lat2(site.pos[0],site.pos[1]) for site in Sites if
site.pos[2]==x)]=0*
* sys2[kwant.builder.HoppingKind((1, 0), lat2, lat2)] = hoppingz
sys2[kwant.builder.HoppingKind((0, 1), lat2, lat2)] = hoppingy*
* #sys2[lat2.neighbors()]=-sigma_0*
* #lead2=kwant.Builder(kwant.TranslationalSymmetry((-1, 0)))
#lead2[(lat2(site.pos[0], site.pos[1]) for site in Sites if
site.pos[2]==x)]=onsite_s #lead2[kwant.builder.HoppingKind((1, 0), lat2,
lat2)] = hoppingz #lead2[kwant.builder.HoppingKind((0, 1), lat2, lat2)]
= hoppingy #sys2.attach_lead(lead2)
#sys2.attach_lead(lead2.reversed()) sys2f=sys2.finalized()
#kwant.plot(sys2f) kwant.plotter.current(sys2f, current)for i in
range(10): Plot(i,psi)*
--
With Best Regards
Naveen Yadav
Ph.D Research Scholar
Deptt. Of Physics & Astrophysics
University Of Delhi.
