Hi there,
I'm trying to simulate a scattering region confined between two
reservoirs(leads) for that purpose I defines a wire with linearly increasing
onsite potentials. Now I want to find the local current density at each site
on the wire but I don't know how to do it. Can anyone guide me through this?
:)
def make_system(a=1, t=1.0, W = 60, L = 100, pot=-0.2):
lat = kwant.lattice.square(a)
sys = kwant.Builder()
def hop(site1, site2, B=0):
# The magnetic field is controlled by the parameter B
x1, y1 = site1.pos
x2, y2 = site2.pos
return -t * exp(0.5j * B * (y1+y2)* (x1-x2))#exp(0.5j * B * (y1-x1))
def potential_prof(i,L,pot):
#potential profile linearly determined here
return (L-i)*pot/L
# Define the scattering region
for i in xrange(L):
for j in xrange(W):
# On-site Hamiltonian
sys[lat(i, j)] = 4 * t+potential_prof(i,L,pot)
sys[kwant.builder.HoppingKind((1, 0), lat, lat)] = hop
sys[kwant.builder.HoppingKind((0, 1), lat, lat)] = hop
sym_left_lead = kwant.TranslationalSymmetry((-a, 0))
left_lead = kwant.Builder(sym_left_lead)
for j in xrange(W):
left_lead[lat(0, j)] = 4 * t+pot
if j > 0:
left_lead[lat(0, j), lat(0, j - 1)] = -t
left_lead[lat(1, j), lat(0, j)] = -t
sys.attach_lead(left_lead)
sym_right_lead = kwant.TranslationalSymmetry((a, 0))
right_lead = kwant.Builder(sym_right_lead)
for j in xrange(W):
right_lead[lat(0, j)] = 4 * t
if j > 0:
right_lead[lat(0, j), lat(0, j - 1)] = -t
right_lead[lat(1, j), lat(0, j)] = -t
sys.attach_lead(right_lead)
# Modify the scattering region
del sys[lat(85, 2)]
del sys[lat(87, 2)]
del sys[lat(86, 3)]
del sys[lat(25, 37)]
del sys[lat(27, 37)]
del sys[lat(26, 38)]
sys = sys.finalized()
return sys
