[Kwant] PyPlot.plot will give the incorrect number

15 May 2021

      Hello

I felt confusing, when I use pyplot.plt.  The data in figure is different from the printed.

There are the codes:

# ================================================================

# Physics background

# ------------------

# Kwant features highlighted

# --------------------------

#  - Numpy matrices as values in Builder

import kwant

import numpy as np

# For plotting

import matplotlib.pyplot as plt

# For matrix support

import tinyarray

import kwant.qsymm

# define Pauli-matrices for convenience

s_0 = tinyarray.array([[1, 0], [0, 1]])

s_x = tinyarray.array([[0, 1], [1, 0]])

s_y = tinyarray.array([[0, -1j], [1j, 0]])

s_z = tinyarray.array([[1, 0], [0, -1]])

mz=0    # AFM

mu=0.0    # stargged chemical potential

n_theta=12

def make_system(constant=1, W=30, L=30, mz=0, m_in=0, mu=0):

    lat = kwant.lattice.honeycomb(a=constant,norbs=2, name=['a', 'b'])

    # a, b = lat.sublattices

    sym = kwant.TranslationalSymmetry(lat.vec((1, 0)))

    syst = kwant.Builder()

    def onsite_a(site,theta):

        return mz*s_z+m_in*(np.cos(theta)*s_x+np.sin(theta)*s_y)+mu*s_0

    def onsite_b(site,theta):

        return  -mz*s_z+m_in*(np.cos(theta)*s_x+np.sin(theta)*s_y)-mu*s_0

    syst[(lat.a(x, y) for x in range(L) for y in range(W))] = onsite_a

    syst[(lat.b(x, y) for x in range(L) for y in range(W))] = onsite_b

    syst[lat.neighbors()] = s_0

    # define lead

    left_sym=kwant.TranslationalSymmetry(lat.vec((1, 0)))

    left_lead=kwant.Builder(left_sym)

    left_lead[(lat.a(0, y) for y in range(W))] = onsite_a

    left_lead[(lat.b(0, y) for y in range(W))] = onsite_b

    left_lead[lat.neighbors()] = s_0

    syst.attach_lead(left_lead)

    syst.attach_lead(left_lead.reversed())

    return syst

def plot_conductance(syst, energy, theta_list):

    # Compute conductance

    data = np.zeros(n_theta)

    num_i=-1

    for theta_i in theta_list:

        num_i=num_i+1

        smatrix = kwant.smatrix(syst, energy, params=dict(theta=theta_i))

        data[num_i]=smatrix.transmission(1, 0)

    plt.figure()

    # x=np.linspace(-1,1,n_theta)

    # data_i=np.linspace(0,0,n_theta)

    # print(x,data_i)

    # plt.plot(x,data_i,'ow')

    print(data)

    plt.plot(theta_list, data)

    plt.xlabel(r'$\theta/\pi$')

    plt.ylabel("conductance [e^2/h]")

    plt.savefig('tran_PHE.jpg')

    #plt.show()

def main():

    syst = make_system(m_in=0.0001)

    # Check that the system looks as intended.

    kwant.plot(syst,file='transport_lattice.pdf')

    syst = syst.finalized()

    theta_num=np.linspace(-np.pi,np.pi,num=n_theta)

    plot_conductance(syst, energy=0.0001,

                     theta_list=theta_num)

if __name__ == '__main__':

    main()

The result would be printed in terminal: [1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.].

However, the figure plotted is wrong.

--

Best Wishes
Jinlong Zhang
jlzhang@163.com

[Kwant] PyPlot.plot will give the incorrect number

张金龙