kwant.builder.FiniteSystem#
- class kwant.builder.FiniteSystem(builder)[source]#
Bases:
_FinalizedBuilderMixin
,FiniteSystem
Finalized
Builder
with leads.Usable as input for the solvers in
kwant.solvers
.- sites[source]#
sites[i]
is theSite
instance that corresponds to the integer-labeled sitei
of the low-level system. The sites are ordered first by their family and then by their tag.- Type:
sequence
- id_by_site[source]#
The inverse of
sites
; maps high-levelSite
instances to their integer label. Satisfiesid_by_site[sites[i]] == i
.- Type:
dict
Methods
- discrete_symmetry(args=(), *, params=None)[source]#
Return the discrete symmetry of the system.
The returned object is an instance of
DiscreteSymmetry
.Providing positional arguments via ‘args’ is deprecated, instead, provide named parameters as a dictionary via ‘params’.
- hamiltonian(i, j, *args, params=None)[source]#
Return the hamiltonian matrix element for sites
i
andj
.If
i == j
, return the on-site Hamiltonian of sitei
.if
i != j
, return the hopping between sitei
andj
.Hamiltonians may depend (optionally) on positional and keyword arguments.
Providing positional arguments via ‘args’ is deprecated, instead, provide named parameters as a dictionary via ‘params’.
- hamiltonian_submatrix(self, args=(), to_sites=None, from_sites=None, sparse=False, return_norb=False, *, params=None)[source]#
Return a submatrix of the system Hamiltonian.
- Parameters:
args (tuple, defaults to empty) – Positional arguments to pass to the
hamiltonian
method. Mutually exclusive with ‘params’.to_sites (sequence of sites or None (default)) –
from_sites (sequence of sites or None (default)) –
sparse (bool) – Whether to return a sparse or a dense matrix. Defaults to
False
.return_norb (bool) – Whether to return arrays of numbers of orbitals. Defaults to
False
.params (dict, optional) – Dictionary of parameter names and their values. Mutually exclusive with ‘args’.
- Returns:
hamiltonian_part (numpy.ndarray or scipy.sparse.coo_matrix) – Submatrix of Hamiltonian of the system.
to_norb (array of integers) – Numbers of orbitals on each site in to_sites. Only returned when
return_norb
is true.from_norb (array of integers) – Numbers of orbitals on each site in from_sites. Only returned when
return_norb
is true.
Notes
The returned submatrix contains all the Hamiltonian matrix elements from
from_sites
toto_sites
. The default forfrom_sites
andto_sites
isNone
which means to use all sites of the system in the order in which they appear.
- precalculate(energy=0, args=(), leads=None, what='modes', *, params=None)[source]#
Precalculate modes or self-energies in the leads.
Construct a copy of the system, with the lead modes precalculated, which may significantly speed up calculations where only the system is changing.
- Parameters:
energy (float) – Energy at which the modes or self-energies have to be evaluated.
args (sequence) – Additional parameters required for calculating the Hamiltionians. Deprecated in favor of ‘params’ (and mutually exclusive with it).
leads (sequence of integers or None) – Numbers of the leads to be precalculated. If
None
, all are precalculated.what ('modes', 'selfenergy', 'all') – The quantitity to precompute. ‘all’ will compute both modes and self-energies. Defaults to ‘modes’.
params (dict, optional) – Dictionary of parameter names and their values. Mutually exclusive with ‘args’.
- Returns:
syst – A copy of the original system with some leads precalculated.
- Return type:
Notes
If the leads are precalculated at certain energy or args values, they might give wrong results if used to solve the system with different parameter values. Use this function with caution.
- validate_symmetries(args=(), *, params=None)[source]#
Check that the Hamiltonian satisfies discrete symmetries.
Applies
validate
to the Hamiltonian, see its documentation for details on the return format.Providing positional arguments via ‘args’ is deprecated, instead, provide named parameters as a dictionary via ‘params’.