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Hi James, Welcome! * Can you be more specific when saying "nothing works"? What exactly goes opposite to your expectations? * Hall conductance: take a look at this thread: http://thread.gmane.org/gmane.comp.science.kwant.user/276 Best, Anton On Tue, Aug 25, 2015 at 1:12 PM, james edward hernandez <kibwiw@yahoo.com.ph> wrote:
Hi all.
I would like to know how to compute Hall conductance in a honeycomb lattice using Kwant. In my attempt, I started with the construction of the honeycomb lattice:
import kwant import matplotlib.pyplot as plt import numpy from cmath import exp from kwant.digest import gauss
lat = kwant.lattice.honeycomb() sys = kwant.Builder()
def rectangle(pos): x, y = pos return 0 < x < 40 and 0 < y < 20
sys[lat.shape(rectangle, (1, 1))] = 0 sys[lat.neighbors()] = -1
sym = kwant.TranslationalSymmetry((-1, 0)) sym.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)])
lead = kwant.Builder(sym)
def lead_shape(pos): x, y = pos return 0 < y < 20
lead[lat.shape(lead_shape, (-1,1))] = 4 lead[lat.neighbors()] = -1
sys.attach_lead(lead) sys.attach_lead(lead.reversed())
My questions are: How to attach another pair of leads at 13 < x < 15 and 23 < x < 25 with y = 10 and y =0? I tried # For the 2nd Lead sym2 = kwant.TranslationalSymmetry((-1, 0))
sym2.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym2.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)])
lead2 = kwant.Builder(sym)
def lead2_shape(pos2): x, y = pos2 return 13 < x < 15, 10 < y < 10
lead[lat.shape(lead2_shape, (1,1))] = 4 lead[lat.neighbors()] = -1
sys.attach_lead(lead2) sys.attach_lead(lead2.reversed())
but nothing works.
Also How to calculate hall conductance from these leads (assuming hopping is by Peierls substitution where t is replaced by an exponential)?
I am very new to the kwant program, as this is for an undergraduate research. Regards, James