kwant.lattice.
Polyatomic
(prim_vecs, basis, name='')¶Bases: object
A Bravais lattice with an arbitrary number of sites in the basis.
Contains Monatomic
sublattices. Note that an instance of Polyatomic
is
not itself a SiteFamily
, only its sublattices are.
Parameters:  prim_vecs : 2d arraylike of floats
basis : 2d arraylike of floats
name : string or sequence of strings


Raises:  ValueError

Methods
neighbors
(n=1, eps=1e08)¶Return nth nearest neighbor hoppings.
Parameters:  n : integer
eps : float


Returns:  hoppings : list of kwant.builder.HopplingKind objects

Notes
The hoppings are ordered lexicographically according to sublattice from which they originate, sublattice on which they end, and their lattice coordinates. Out of the two equivalent hoppings (a hopping and its reverse) only the lexicographically larger one is returned.
shape
(function, start)¶Return a key for all the lattice sites inside a given shape.
The object returned by this method is primarily meant to be used as a
key for indexing kwant.Builder
instances. See example below.
Parameters:  function : callable
start : 1d arraylike


Returns:  shape_sites : function 
Notes
When the function returned by this method is called, a floodfill algorithm finds and yields all the lattice sites inside the specified shape starting from the specified position.
A Symmetry
or Builder
may be passed as
sole argument when calling the function returned by this method. This
will restrict the floodfill to the fundamental domain of the symmetry
(or the builder’s symmetry). Note that unless the shape function has
that symmetry itself, the result may be unexpected.
Examples
>>> def circle(pos):
... x, y = pos
... return x**2 + y**2 < 100
...
>>> lat = kwant.lattice.honeycomb()
>>> sys = kwant.Builder()
>>> sys[lat.shape(circle, (0, 0))] = 0
>>> sys[lat.neighbors()] = 1
vec
(int_vec)¶Return the coordinates of a Bravais lattice vector in real space.
Parameters:  vec : integer vector 

Returns:  output : real vector 
wire
(center, radius)¶Return a key for all the lattice sites inside an infinite cylinder.
This method makes it easy to define cylindrical (2d: rectangular) leads
that point in any direction. The object returned by this method is
primarily meant to be used as a key for indexing kwant.Builder
instances. See example below.
Parameters:  center : 1d arraylike of floats
radius : float


Notes
The function returned by this method is to be called with a
TranslationalSymmetry instance (or a
Builder
instance whose symmetry is used then) as sole
argument. All the lattice sites (in the fundamental domain of the
symmetry) inside the specified infinite cylinder are yielded. The
direction of the cylinder is determined by the symmetry.
Examples
>>> lat = kwant.lattice.honeycomb()
>>> sym = kwant.TranslationalSymmetry(lat.a.vec((2, 1)))
>>> lead = kwant.Builder(sym)
>>> lead[lat.wire((0, 5), 5)] = 0
>>> lead[lat.neighbors()] = 1
Attributes
prim_vecs
¶(sequence of vectors) Primitive vectors
prim_vecs[i]` is the ith primitive basis vector of the lattice displacement of the lattice origin from the real space coordinates origin.