def test_honeycomb():
lat = kwant.lattice.honeycomb(norbs=1)
# Test simple honeycomb model with constant terms
# Add discrete symmetries to the kwant builder as well, to check that they are
# returned as well.
syst = kwant.Builder(symmetry=TranslationalSymmetry(*lat.prim_vecs))
syst[lat.a(0, 0)] = 1
syst[lat.b(0, 0)] = 1
syst[lat.neighbors(1)] = -1
H = builder_to_model(syst)
sg, cs = symmetries(H, hexagonal(sympy_R=False), prettify=True)
assert len(sg) == 24
assert len(cs) == 0
# Test simple honeycomb model with value functions
syst = kwant.Builder(symmetry=TranslationalSymmetry(*lat.prim_vecs))
syst[lat.a(0, 0)] = lambda site, ma: ma
syst[lat.b(0, 0)] = lambda site, mb: mb
syst[lat.neighbors(1)] = lambda site1, site2, t: t
H = builder_to_model(syst)
sg, cs = symmetries(H, hexagonal(sympy_R=False), prettify=True)
assert len(sg) == 12
assert len(cs) == 0
def test_higher_dim():
# Test 0D finite system
lat = kwant.lattice.cubic(norbs=1)
syst = kwant.Builder()
syst[lat(0, 0, 0)] = 1
syst[lat(1, 1, 0)] = 1
syst[lat(0, 1, 1)] = 1
syst[lat(1, 0, -1)] = 1
syst[lat(0, 0, 0), lat(1, 1, 0)] = -1
syst[lat(0, 0, 0), lat(0, 1, 1)] = -1
syst[lat(0, 0, 0), lat(1, 0, -1)] = -1
H = builder_to_model(syst)
sg, cs = symmetries(H, prettify=True)
assert len(sg) == 2
assert len(cs) == 5
# Test triangular lattice system embedded in 3D
sym = TranslationalSymmetry([1, 1, 0], [0, 1, 1])
lat = kwant.lattice.cubic(norbs=1)
syst = kwant.Builder(symmetry=sym)
syst[lat(0, 0, 0)] = 1
syst[lat(0, 0, 0), lat(1, 1, 0)] = -1
syst[lat(0, 0, 0), lat(0, 1, 1)] = -1
syst[lat(0, 0, 0), lat(1, 0, -1)] = -1
H = builder_to_model(syst)
sg, cs = symmetries(H, hexagonal(sympy_R=False), prettify=True)
assert len(sg) == 24
assert len(cs) == 0
def test_real_space_basis():
lat = kwant.lattice.honeycomb(norbs=[1, 1])
sym = kwant.TranslationalSymmetry(lat.vec((1, 0)), lat.vec((0, 1)))
bulk = kwant.Builder(sym)
bulk[[lat.a(0, 0), lat.b(0, 0)]] = 0
bulk[lat.neighbors()] = 1
# Including real space symmetries
symmetries = find_builder_symmetries(bulk)
hex_group_2D = hexagonal()
hex_group_2D = set(
PointGroupElement(
np.array(s.R).astype(float), s.conjugate, s.antisymmetry, None)
for s in hex_group_2D)
assert len(symmetries) == len(hex_group_2D)
assert all([
s1 in symmetries and s2 in hex_group_2D
for s1, s2 in zip(hex_group_2D, symmetries)
])
# Only onsite discrete symmetries
symmetries = find_builder_symmetries(bulk, spatial_symmetries=False)
onsites = [
PointGroupElement(np.eye(2), True, False, None), # T
PointGroupElement(np.eye(2), True, True, None), # P
PointGroupElement(np.eye(2), False, True, None), # C
PointGroupElement(np.eye(2), False, False, None)
] # I
assert len(symmetries) == len(onsites)
assert all([
s1 in symmetries and s2 in onsites
for s1, s2 in zip(onsites, symmetries)
])