fluxes = np.linspace(0, 5, 100)

def make_system(a=1, t=1.5, w=15, d=30):

lat = kwant.lattice.square(a)

syst = kwant.Builder()

def onsite(site, U0, salt):

return U0 * (uniform(repr(site), repr(salt)) - 0.5) + 4*t

syst[(lat(x, y) for x in range(w) for y in range(d))] = onsite

def hopping(site_i, site_j, phi):

xi, yi = site_i.pos

xj, yj = site_j.pos

if yi == yj:

return -t

if xi == xj:

return -0.001 * t * exp(-0.5j * phi * (xi + xj) * (yi - yj))

syst[lat.neighbors()] = hopping

lead = kwant.Builder(kwant.TranslationalSymmetry((0, -a)))

lead[(lat(j, 0) for j in range(w))] = 4 * t

lead[lat.neighbors()] = hopping

syst.attach_lead(lead)

syst.attach_lead(lead.reversed())

return syst

def plot_conductance(syst):

temp = 0.01

w=15

d=30

U0=0

salt = 0.2

phis = np.linspace(0, (2 * pi / w) * 5, 100)

count = 0

values = []

for phi in phis:

count += 1

ham_mat = syst.hamiltonian_submatrix(params=dict(phi=phi, U0=U0, salt=salt), sparse=True)

evals = np.real(np.sort(np.linalg.eigvals(ham_mat.todense())))

EF = evals[int(len(evals) / 2)]

liste = []

for k in range(0,len(evals)):

energy = evals[k]

if EF-temp <= energy <= EF+temp:

df = np.real(exp((energy - EF) / temp) / (temp * (exp((energy - EF) / temp) + 1) ** 2))

Smatrix = kwant.smatrix(syst, energy, params=dict(phi=phi, U0=U0, salt=salt))

liste.append(Smatrix.transmission(0,1)*df)

val = sum(liste)/(len(liste))

values.append(val/(w*d))

print(count)

plt.plot(fluxes,values, label = w)

plt.grid(True)

plt.title("Conductance eqhop temp=0.1")

plt.legend()

plt.ylabel("G_[G_0]")

plt.xlabel(r'$\phi [2\pi / L]$')

plt.show()

def main():

syst = make_system()

syst = syst.finalized()

plot_conductance(syst)

if __name__ == "__main__":

main()