Nanoribbons

See the Shape and symmetry tutorial page for more details on nanoribbon construction. These are just a few quick examples.

Bilayer graphene

Source code

"""Bilayer graphene nanoribbon with zigzag edges"""
import pybinding as pb
import matplotlib.pyplot as plt
from pybinding.repository import graphene
from math import pi, sqrt

pb.pltutils.use_style()


def bilayer_graphene():
    """Bilayer lattice in the AB-stacked form (Bernal-stacked)"""
    lat = pb.Lattice(a1=[graphene.a, 0], a2=[0.5*graphene.a, 0.5*sqrt(3)*graphene.a])

    c0 = 0.335  # [nm] interlayer spacing
    lat.add_sublattices(('A1', [0,  -graphene.a_cc/2,   0]),
                        ('B1', [0,   graphene.a_cc/2,   0]),
                        ('A2', [0,   graphene.a_cc/2, -c0]),
                        ('B2', [0, 3*graphene.a_cc/2, -c0]))
    lat.register_hopping_energies({'t': graphene.t, 't_layer': -0.4})
    lat.add_hoppings(
        # layer 1
        ([ 0,  0], 'A1', 'B1', 't'),
        ([ 1, -1], 'A1', 'B1', 't'),
        ([ 0, -1], 'A1', 'B1', 't'),
        # layer 2
        ([ 0,  0], 'A2', 'B2', 't'),
        ([ 1, -1], 'A2', 'B2', 't'),
        ([ 0, -1], 'A2', 'B2', 't'),
        # interlayer
        ([ 0,  0], 'B1', 'A2', 't_layer')
    )
    lat.min_neighbors = 2
    return lat

model = pb.Model(
    bilayer_graphene(),
    pb.rectangle(1.3),  # nm
    pb.translational_symmetry(a1=True, a2=False)
)
model.plot()
model.lattice.plot_vectors(position=[-0.6, 0.3])  # nm
plt.show()

solver = pb.solver.lapack(model)
bands = solver.calc_bands(-pi/graphene.a, pi/graphene.a)
bands.plot(point_labels=[r"$-\pi / a$", r"$\pi / a$"])
plt.show()