kwant.system.
SiteFamily
(canonical_repr, name, norbs)[source]¶Bases: object
Abstract base class for site families.
Site families are the ‘type’ of Site
objects. Within a family, individual
sites are uniquely identified by tags. Valid tags must be hashable Python
objects, further details are up to the family.
Site families must be immutable and fully defined by their initial
arguments. They must inherit from this abstract base class and call its
__init__ function providing it with two arguments: a canonical
representation and a name. The canonical representation will be returned as
the objects representation and must uniquely identify the site family
instance. The name is a string used to distinguish otherwise identical site
families. It may be empty. norbs
defines the number of orbitals
on sites associated with this site family; it may be None, in which case
the number of orbitals is not specified.
All site families must define either ‘normalize_tag’ or ‘normalize_tags’, which brings a tag (or, in the latter case, a sequence of tags) to the standard format for this site family.
Site families may also implement methods pos(tag)
and
positions(tags)
, which return a vector of realspace coordinates or an
array of vectors of realspace coordinates of the site(s) belonging to this
family with the given tag(s). These methods are used in plotting routines.
positions(tags)
should return an array with shape (N, M)
where
N
is the length of tags
, and M
is the realspace dimension.
If the norbs
of a site family are provided, and sites of this family
are used to populate a Builder
, then the associated
Hamiltonian values must have the correct shape. That is, if a site family
has norbs = 2
, then any on-site terms for sites belonging to this
family should be 2x2 matrices. Similarly, any hoppings to/from sites
belonging to this family must have a matrix structure where there are two
rows/columns. This condition applies equally to Hamiltonian values that
are given by functions. If this condition is not satisfied, an error will
be raised.
Methods
normalize_tag
(tag)[source]¶Return a normalized version of the tag.
Raises TypeError or ValueError if the tag is not acceptable.
Return a normalized version of the tags.
Raises TypeError or ValueError if the tags are not acceptable.