import sys

sys.path.append("../../code")
from init_mooc_nb import *

init_notebook()
%output size=150
pi_ticks = [(-np.pi, r"$-\pi$"), (0, "0"), (np.pi, r"$\pi$")]


def Qi_Wu_Zhang(w=None):
    def onsite(site, p):
        return -p.mu * pauli.sz

    def hopx(site1, site2, p):
        return -0.5j * p.delta * pauli.sy - p.t * pauli.sz

    def hopy(site1, site2, p):
        return -1j * p.gamma * pauli.sx - p.gamma * pauli.sz

    lat = kwant.lattice.square()

    if w == None:
        syst = kwant.Builder(kwant.TranslationalSymmetry(*lat.prim_vecs))
        syst[lat.shape(lambda pos: True, (0, 0))] = onsite
    else:

        def ribbon_shape(pos):
            return 0 <= pos[1] < w

        sym = kwant.TranslationalSymmetry((1, 0))
        syst = kwant.Builder(sym)
        syst[lat.shape(ribbon_shape, (0, 0))] = onsite

    syst[kwant.HoppingKind((1, 0), lat)] = hopx
    syst[kwant.HoppingKind((0, 1), lat)] = hopy
    return syst


def title(p):
    title = r"$t={:.2}$, $\mu={:.2}$, $\Delta={:.2}$, $\gamma={:.2}$"
    title = title.format(p.t, p.mu, p.delta, p.gamma)
    return title

Populated the namespace with:
np, matplotlib, kwant, holoviews, init_notebook, SimpleNamespace, pprint_matrix, scientific_number, pretty_fmt_complex, plt, pf, display_html
from code/edx_components:
MoocVideo, MoocDiscussion, MoocCheckboxesAssessment, MoocMultipleChoiceAssessment, MoocSelfAssessment
from code/functions:
spectrum, hamiltonian_array, h_k, pauli
Using kwant 1.4.2 and holoviews 1.13.2
Executed on 2020-06-07 at 08:23:16.935697.