Dear Declan,
The leads have translation invariance in the x-direction. You should not
put a condition such as (0 <= x <= L_lead ) in your lead_shape function.
You can notice that kwant does not plot the leads are you expect them to be.
Please change your function to:
def lead_shape(site):
(x, y) = site.pos
return 0 <= y <= W_lead
I hope this helps,
Adel
On Mon, Jun 1, 2020 at 10:04 PM <declanburk...@gmail.com> wrote:
> import matplotlib.pyplot as plt
> import kwant
> import kwant.continuum
>
>
>
> syst = kwant.Builder()
> print(syst)
>
> a = 10 # angstroms
> norbs = 2 # 2 atomic orbitals * 2 spins * particle-hole
> at = kwant.lattice.cubic(a, norbs=norbs)
> #chain (1D), cubic (3D), triangular, honeycomb, kagome
> #print(lat)
>
> ham = ("alpha * (k_x * sigma_x - k_y * sigma_y)"
> "+ (m + beta * kk) * sigma_z"
> "+ (gamma * kk + U) * sigma_0")
> subs = {"kk": "k_x**2 + k_y**2"}
>
>
> ham_discretized = kwant.continuum.discretize(ham, locals=subs, grid=a)
> print(ham_discretized)
>
> # dimensions in angstroms
> L = 300
> W = 50
> H = 100
>
> def syst_shape(site):
> (x, y) = site.pos
> return (0 <= x <= L and 0 <= y <= W)
>
> syst.fill(ham_discretized, syst_shape, (0, 0));
>
> lead_left = kwant.Builder(kwant.TranslationalSymmetry((-a, 0)))
> lead_right = kwant.Builder(kwant.TranslationalSymmetry((a, 0)))
>
>
> L_lead = L
> W_lead = W
>
> def lead_shape(site):
> (x, y) = site.pos
> return (0 <= x <= L_lead and 0 <= y <= W_lead)
>
> lead_left.fill(ham_discretized, lead_shape, (0, 0));
> lead_right.fill(ham_discretized, lead_shape, (L, 0));
>
> syst_leads = syst
>
> syst_leads.attach_lead(lead_left)
> syst_leads.attach_lead(lead_right)
>
> kwant.plot(syst_leads);
>
> syst = syst.finalized()
> syst_leads = syst_leads.finalized()
>
> params = dict(alpha=0.365, beta=0.686, gamma=0.512, m=-0.01, U=-0)
>
>
> psi = kwant.wave_function(syst, energy=params['m'], params=params)(0)
> J = kwant.operator.Current(syst).bind(params=params)
> current = sum(J(p) for p in psi)
> kwant.plotter.current(syst, current)
>
>
>
> kwant.plotter.bands(syst_leads.leads[0], params=params);
>
> energies = []
> data = []
> for ie in range(100):
> energy = ie * 0.01
>
> # compute the scattering matrix at a given energy
> smatrix = kwant.smatrix(syst, energy)
>
> # compute the transmission probability from lead 0 to
> # lead 1
> energies.append(energy)
> data.append(smatrix.transmission(0,1)(0,0))
>
>
> plt.figure()
> plt.plot(energies, data)
> plt.xlabel("energy [t]")
> plt.ylabel("conductance [e^2/h]")
> plt.show()
>
--
Abbout Adel
