def make_system():
sys = kwant.Builder()
sys[graphene.shape(disk, (0, 0))] = onsite
sys[graphene.neighbors()] = -s0
sys[[kwant.builder.HoppingKind(*hopping)
for hopping in nnn_hoppings]] = spin_orbit_v
sys[kwant.HoppingKind((0, 0), a, b)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), a, b)] = hop_ras_e2
sys[kwant.HoppingKind((-1, 1), a, b)] = hop_ras_e3
lead = kwant.Builder(kwant.TranslationalSymmetry((-1, 0)))
lead[graphene.shape((lambda pos: abs(pos[1]) < 10), (0, 0))] = onsite_lead
lead[graphene.neighbors()] = -s0
lead[[kwant.builder.HoppingKind(*hopping)
for hopping in nnn_hoppings]] = spin_orbit_v_lead
sys.attach_lead(lead)
sys.attach_lead(lead.reversed())
return sys.finalized()
def make_system():
sys = kwant.Builder()
sys[lat_u.shape(disk,(0,0))] = onsite
sys[lat_d.shape(disk,(0,0))] = onsite
sys[lat_u.neighbors()] = 1
sys[lat_d.neighbors()] = 1
sys[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppings]] = nnn
sys[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppingsd]] = nnn
sys[kwant.HoppingKind((0, 0), a,bd)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), a,bd)] = hop_ras_e2
sys[kwant.HoppingKind((-1, 1), a,bd)] = hop_ras_e3
sys[kwant.HoppingKind((0, 0), ad,b)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), ad,b)] = hop_ras_e2
sys[kwant.HoppingKind((-1, 1), ad,b)] = hop_ras_e3
# sym_left = kwant.TranslationalSymmetry((-1, 0))
# lead0 = kwant.Builder(sym_left)
# lead0[lat_u.shape((lambda pos: abs(pos[1]) < width), (0, 0))]=onsite#1
# lead0[lat_u.neighbors()] = 1
# lead0[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppings]] = nnn
## # left hole lead
# lead1 = kwant.Builder(sym_left)
# lead1[lat_d.shape((lambda pos: abs(pos[1]) < width), (0, 0))]=onsite#1
# lead1[lat_d.neighbors()] = 1
# lead1[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppingsd]] = nnn
#
# sys.attach_lead(lead0) #spin up
# sys.attach_lead(lead1) #spin down
# sys.attach_lead(lead0.reversed()) #lead3 spin up
# sys.attach_lead(lead1.reversed()) #lead4 spin down
sym0u = kwant.TranslationalSymmetry((-1,0))
sym0u.add_site_family(lat_u.sublattices[0], other_vectors=[(-1, 2)])
sym0u.add_site_family(lat_u.sublattices[1], other_vectors=[(-1, 2)])
lead0_u = kwant.Builder(sym0u)
lead0_u[lat_u.shape(lead0_shape,(0,1))]= onsite # 1#
lead0_u[lat_u.neighbors()] = 1
lead0_u[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppings]] = nnn
sys.attach_lead(lead0_u)
#================================left_down0=====================================
sym0d = kwant.TranslationalSymmetry((-1,0))
sym0d.add_site_family(lat_d.sublattices[0], other_vectors=[(-1, 2)])
sym0d.add_site_family(lat_d.sublattices[1], other_vectors=[(-1, 2)])
lead0_d = kwant.Builder(sym0d)
lead0_d[lat_d.shape(lead0_shape,(0,1))]= onsite # 1#
lead0_d[lat_d.neighbors()] = 1
lead0_d[[kwant.builder.HoppingKind(*hopping) for hopping in nnn_hoppingsd]] = nnn
sys.attach_lead(lead0_d)
sys.attach_lead(lead0_u.reversed())
sys.attach_lead(lead0_d.reversed())
return sys
def test_operator_construction():
lat, syst = _random_square_system(3)
fsyst = syst.finalized()
N = len(fsyst.sites)
# test construction failure if norbs not given
latnone = kwant.lattice.chain()
syst[latnone(0)] = 1
for A in opservables:
raises(ValueError, A, syst.finalized())
del syst[latnone(0)]
# test construction failure when dimensions of onsite do not match
for A in opservables:
raises(ValueError, A, fsyst, onsite=np.eye(2))
# test that error is raised when input array is the wrong size
for A in opservables:
a = A(fsyst)
kets = list(map(np.ones, [(0, ), (N - 1, ), (N + 1, ), (N, 1)]))
for ket in kets:
raises(ValueError, a, ket)
raises(ValueError, a, ket, ket)
raises(ValueError, a.act, ket)
raises(ValueError, a.act, ket, ket)
# Test failure on non-hermitian
for A in (ops.Density, ops.Current, ops.Source):
raises(ValueError, A, fsyst, 1j)
# Test output dtype
ket = np.ones(len(fsyst.sites))
for A in (ops.Density, ops.Current, ops.Source):
a = A(fsyst)
a_nonherm = A(fsyst, check_hermiticity=False)
assert a(ket, ket).dtype == np.complex128
assert a(ket).dtype == np.float64
assert a_nonherm(ket, ket).dtype == np.complex128
assert a_nonherm(ket).dtype == np.complex128
# test construction with different numbers of orbitals
lat2 = kwant.lattice.chain(norbs=2)
extra_sites = [lat2(i) for i in range(N)]
syst[extra_sites] = np.eye(2)
syst[zip(fsyst.sites, extra_sites)] = ta.matrix([1, 1])
for A in opservables:
raises(ValueError, A, syst.finalized(), onsite=np.eye(2))
A(syst.finalized())
A.onsite == np.eye(2)
del syst[extra_sites]
check = [(ops.Density, np.arange(N).reshape(-1, 1), ta.identity(1)),
(ops.Current, np.array(list(fsyst.graph)), ta.identity(1)),
(ops.Source, np.arange(N).reshape(-1, 1), ta.identity(1))]
# test basic construction
for A, where, onsite in check:
a = A(fsyst)
assert np.all(np.asarray(a.where) == where)
assert all(a.onsite == onsite for i in range(N))
# test construction with dict `onsite`
for A in opservables:
B = A(fsyst, {lat: 1})
assert all(B.onsite(i) == 1 for i in range(N))
# test construction with a functional onsite
for A in opservables:
B = A(fsyst, lambda site: site.pos[0]) # x-position operator
assert all(B.onsite(i) == fsyst.sites[i].pos[0] for i in range(N))
# test construction with `where` given by a sequence
where = [lat(2, 2), lat(1, 1)]
fwhere = tuple(fsyst.id_by_site[s] for s in where)
A = ops.Density(fsyst, where=where)
assert np.all(np.asarray(A.where).reshape(-1) == fwhere)
where = [(lat(2, 2), lat(1, 2)), (lat(0, 0), lat(0, 1))]
fwhere = np.asarray([(fsyst.id_by_site[a], fsyst.id_by_site[b])
for a, b in where])
A = ops.Current(fsyst, where=where)
assert np.all(np.asarray(A.where) == fwhere)
# test construction with `where` given by a function
tag_list = [(1, 0), (1, 1), (1, 2)]
def where(site):
return site.tag in tag_list
A = ops.Density(fsyst, where=where)
assert all(fsyst.sites[A.where[w, 0]].tag in tag_list
for w in range(A.where.shape[0]))
where_list = set(kwant.HoppingKind((1, 0), lat)(syst))
fwhere_list = set(
(fsyst.id_by_site[a], fsyst.id_by_site[b]) for a, b in where_list)
def where(a, b):
return (a, b) in where_list
A = ops.Current(fsyst, where=where)
assert all((a, b) in fwhere_list for a, b in A.where)
# test that `sum` is passed to constructors correctly
for A in opservables:
A(fsyst, sum=True).sum == True
def test_fd_mismatch():
# The fundamental domains of the two 1D symmetries that make up T are
# incompatible. This produced a bug where certain systems could be wrapped
# around in all directions, but could not be wrapped around when 'keep' is
# provided.
sqrt3 = np.sqrt(3)
lat = kwant.lattice.general([(sqrt3, 0), (-sqrt3 / 2, 1.5)])
T = kwant.TranslationalSymmetry((sqrt3, 0), (0, 3))
syst1 = kwant.Builder(T)
syst1[lat(1, 1)] = syst1[lat(0, 1)] = 1
syst1[lat(1, 1), lat(0, 1)] = 1
syst2 = kwant.Builder(T)
syst2[lat(0, 0)] = syst2[lat(0, -1)] = 1
syst2[lat(0, 0), lat(0, -1)] = 1
# combine the previous two
syst3 = kwant.Builder(T)
syst3.update(syst1)
syst3.update(syst2)
for syst in (syst1, syst2, syst3):
wraparound(syst)
wraparound(syst, keep=0)
wraparound(syst, keep=1)
## Test that spectrum of non-trivial system (including above cases)
## is the same, regardless of the way in which it is wrapped around
lat = kwant.lattice.general([(sqrt3, 0), (-sqrt3 / 2, 1.5)],
[(sqrt3 / 2, 0.5), (0, 1)])
a, b = lat.sublattices
T = kwant.TranslationalSymmetry((3 * sqrt3, 0), (0, 3))
syst = kwant.Builder(T)
syst[(l(i, j) for i in range(-1, 2) for j in range(-1, 2)
for l in (a, b))] = 0
syst[kwant.HoppingKind((0, 0), b, a)] = -1j
syst[kwant.HoppingKind((1, 0), b, a)] = 2j
syst[kwant.HoppingKind((0, 1), a, b)] = -2j
def spectrum(syst, keep):
syst = wraparound(syst, keep=keep).finalized()
ks = ('k_x', 'k_y', 'k_z')
if keep is None:
def _(*args):
params = dict(zip(ks, args))
return np.linalg.eigvalsh(
syst.hamiltonian_submatrix(params=params))
else:
def _(*args):
params = dict(zip(ks, args))
kext = params.pop(ks[keep])
B = kwant.physics.Bands(syst, params=params)
return B(kext)
return _
spectra = [spectrum(syst, keep) for keep in (None, 0, 1)]
# Check that spectra are the same at k=0. Checking finite k
# is more tricky, as we would also need to transform the k vectors
E_k = np.array([spec(0, 0) for spec in spectra]).transpose()
assert all(np.allclose(E, E[0]) for E in E_k)
# Test square lattice with oblique unit cell
lat = kwant.lattice.general(np.eye(2))
translations = kwant.lattice.TranslationalSymmetry([2, 2], [0, 2])
syst = kwant.Builder(symmetry=translations)
syst[lat.shape(lambda site: True, [0, 0])] = 1
syst[lat.neighbors()] = 1
# Check that spectra are the same at k=0.
spectra = [spectrum(syst, keep) for keep in (None, 0, 1)]
E_k = np.array([spec(0, 0) for spec in spectra]).transpose()
assert all(np.allclose(E, E[0]) for E in E_k)
# Test Rocksalt structure
# cubic lattice that contains both sublattices
lat = kwant.lattice.general(np.eye(3))
# Builder with FCC translational symmetries.
translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, 0, 1],
[0, 1, 1])
syst = kwant.Builder(symmetry=translations)
syst[lat(0, 0, 0)] = 1
syst[lat(0, 0, 1)] = -1
syst[lat.neighbors()] = 1
# Check that spectra are the same at k=0.
spectra = [spectrum(syst, keep) for keep in (None, 0, 1, 2)]
E_k = np.array([spec(0, 0, 0) for spec in spectra]).transpose()
assert all(np.allclose(E, E[0]) for E in E_k)
# Same with different translation vectors
translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, -1, 0],
[0, 1, 1])
syst = kwant.Builder(symmetry=translations)
syst[lat(0, 0, 0)] = 1
syst[lat(0, 0, 1)] = -1
syst[lat.neighbors()] = 1
# Check that spectra are the same at k=0.
spectra = [spectrum(syst, keep) for keep in (None, 0, 1, 2)]
E_k = np.array([spec(0, 0, 0) for spec in spectra]).transpose()
assert all(np.allclose(E, E[0]) for E in E_k)
# Test that spectrum in slab geometry is identical regardless of choice of unit
# cell in rocksalt structure
def shape(site):
return abs(site.tag[2]) < 4
lat = kwant.lattice.general(np.eye(3))
# First choice: primitive UC
translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, -1, 0],
[1, 0, 1])
syst = kwant.Builder(symmetry=translations)
syst[lat(0, 0, 0)] = 1
syst[lat(0, 0, 1)] = -1
# Set all the nearest neighbor hoppings
for d in [[1, 0, 0], [-1, 0, 0], [0, 1, 0], [0, -1, 0], [0, 0, 1],
[0, 0, -1]]:
syst[(lat(0, 0, 0), lat(*d))] = 1
wrapped = kwant.wraparound.wraparound(syst, keep=2)
finitewrapped = kwant.Builder()
finitewrapped.fill(wrapped, shape, start=np.zeros(3))
sysf = finitewrapped.finalized()
spectrum1 = [
np.linalg.eigvalsh(
sysf.hamiltonian_submatrix(params=dict(k_x=k, k_y=0)))
for k in np.linspace(-np.pi, np.pi, 5)
]
# Second choice: doubled UC with third translation purely in z direction
translations = kwant.lattice.TranslationalSymmetry([1, 1, 0], [1, -1, 0],
[0, 0, 2])
syst = kwant.Builder(symmetry=translations)
syst[lat(0, 0, 0)] = 1
syst[lat(0, 0, 1)] = -1
syst[lat(1, 0, 1)] = 1
syst[lat(-1, 0, 0)] = -1
for s in np.array([[0, 0, 0], [1, 0, 1]]):
for d in np.array([[1, 0, 0], [-1, 0, 0], [0, 1, 0], [0, -1, 0],
[0, 0, 1], [0, 0, -1]]):
syst[(lat(*s), lat(*(s + d)))] = 1
wrapped = kwant.wraparound.wraparound(syst, keep=2)
finitewrapped = kwant.Builder()
finitewrapped.fill(wrapped, shape, start=np.zeros(3))
sysf = finitewrapped.finalized()
spectrum2 = [
np.linalg.eigvalsh(
sysf.hamiltonian_submatrix(params=dict(k_x=k, k_y=0)))
for k in np.linspace(-np.pi, np.pi, 5)
]
assert np.allclose(spectrum1, spectrum2)
def hop_ras_e2_d(site1,site2,Lambda_R=Lambda_R):
return 1j*Lambda_R*(0.5 - 1j*sqrt(3)/2.0)
def hop_ras_e3_d(site1,site2,Lambda_R=Lambda_R):
return 1j*Lambda_R*(0.5 + 1j*sqrt(3)/2.0)
sys[lat_u.shape(Rectangle,(0,1))]=onsite #even with 0 onsite potential, we need to use the zero matrix and not a scalar.
sys[lat_d.shape(Rectangle,(0,1))]=onsite
sys[lat_u.neighbors()] = 1
sys[lat_d.neighbors()] = 1
sys[kwant.HoppingKind((0, 0), a,d)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), a,d)] = hop_ras_e2_u
sys[kwant.HoppingKind((-1, 1), a,d)] = hop_ras_e3_u
sys[kwant.HoppingKind((0, 0), c,b)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), c,b)] = hop_ras_e2_d
sys[kwant.HoppingKind((-1, 1), c,b)] = hop_ras_e3_d
#Here we chose the clockwise Vij which are +1 (as retuned by Hop_value). The other ones (-1) will be given directly
#by the hermeticity of the Hamiltonian
hoppings1_u = (((1, 0), a,a), ((-1, 1), a,a), ((0, -1), a,a))
hoppings2_u = (((1, 0), b,b), ((-1, 1), b,b), ((0, -1), b,b))
hoppings1_d = (((1, 0), c,c), ((-1, 1), c,c), ((0, -1), c,c))
hoppings2_d = (((1, 0), d,d), ((-1, 1), d,d), ((0, -1), d,d))
sys[[kwant.builder.HoppingKind(*hopping) for hopping in hoppings1_u]] = Hop_Value_u
def hop_ras_e2(site1, site2, Lambda_R=Lambda_R, t1=1):
return t1 * sigma_0 + 1j * Lambda_R * (0.5 * sigma_x -
sqrt(3) / 2.0 * sigma_y)
def hop_ras_e3(site1, site2, Lambda_R=Lambda_R, t1=1):
return t1 * sigma_0 + 1j * Lambda_R * (0.5 * sigma_x +
sqrt(3) / 2.0 * sigma_y)
sys[lat.shape(
Rectangle, (0, 1)
)] = onsite #even with 0 onsite potential, we need to use the zero matrix and not a scalar.
#sys[lat.neighbors()]=t1*sigma_0
sys[kwant.HoppingKind((0, 0), a, b)] = hop_ras_e1
sys[kwant.HoppingKind((0, 1), a, b)] = hop_ras_e2
sys[kwant.HoppingKind((-1, 1), a, b)] = hop_ras_e3
#Here we chose the clockwise Vij which are +1 (as retuned by Hop_value). The other ones (-1) will be given directly
#by the hermeticity of the Hamiltonian
hoppings1 = (((1, 0), a, a), ((-1, 1), a, a), ((0, -1), a, a))
hoppings2 = (((1, 0), b, b), ((-1, 1), b, b), ((0, -1), b, b))
sys[[kwant.builder.HoppingKind(*hopping) for hopping in hoppings1]] = Hop_Value
sys[[kwant.builder.HoppingKind(*hopping) for hopping in hoppings2]] = Hop_Value
#==========================left==================================
def lead_shape(pos, ly=ly):
x, y = pos
return 1 <= y < ly
