hi Anant,
could you explain in a bit more detail what you are trying to accomplish?
which model are you using specifically? Perhaps you made a mistake
implementing the tight binding hamiltonian?
cheers,
Robert
On Sat, Nov 22, 2014 at 1:27 PM, ANANT
hello everyone, I am trying to simulate the Kane and mele like crossover of bands in Zigzag geometry. But my bans are not spillting or not I dont get.Bcoz bandstructure show that they are overlapping at all,as shown by colors.Here is my code. # -*- coding: utf-8 -*- # <nbformat>3.0</nbformat>
# <codecell>
#required files are imported import kwant import matplotlib.pyplot import math import numpy as np from cmath import exp import tinyarray
# <codecell>
#lattice defined A,B are sublattices. lat = kwant.lattice.general([(2.46,0), (1.23,1.23*math.sqrt(3))],[(0,0), (0,2.46/ math.sqrt(3))]) A,B= lat.sublattices # All pauli matrices to define spin degree of freedom. s_0=np.identity(2) s_z =np.array([[1, 0], [0, -1]]) s_x = np.array([[0, 1], [1, 0]]) s_y = np.array([[0, -1j], [1j, 0]])
for x in xrange(1): def make(a=50,b=11,t=1,alpha =.09): sym0 = kwant.TranslationalSymmetry(lat.vec((-1,0))) #system building def shape(pos): x, y = pos return (0<= y <=b) sys = kwant.Builder(sym0) #onsite enegies for j in range(b): sys[A(0,j+1)] =.1*s_0 sys[B(0,j)] = -.1*s_0 sys[kwant.builder.HoppingKind((0, 0), A,B )]= - t *s_0 + 1j * alpha *s_z # hopping in y direction sys[kwant.builder.HoppingKind((-1,1), A,B )] =-t *s_0 - 1j * alpha *s_x# hopping in x direction sys[kwant.builder.HoppingKind((0,1), A,B )] = -t *s_0 + 1j * alpha *s_y# hopping in x direction #sys[lat.neighbors()]= -t #sys[lat.neighbors()]= -2.6*s_z return sys #main() function call def main(): sys= make().finalized() #plotting a band structure kwant.plotter.bands(sys,momenta= np.linspace(-5,5,1000),show = False) matplotlib.pyplot.xlabel("S_momentum") matplotlib.pyplot.ylabel("S_energy [t]") matplotlib.pyplot.show() if __name__ == '__main__': main()