kwant.builder.FiniteSystem

class kwant.builder.FiniteSystem(builder)

Finalized Builder with leads.

Usable as input for the solvers in kwant.solvers.

Attributes

sitessequence

sites[i] is the Site instance that corresponds to the integer-labeled site i of the low-level system. The sites are ordered first by their family and then by their tag.

id_by_sitedict

The inverse of sites; maps high-level Site instances to their integer label. Satisfies id_by_site[sites[i]] == i.

Methods

discrete_symmetry(args=(), *, params=None)

Return the discrete symmetry of the system.

Providing positional arguments via ‘args’ is deprecated, instead, provide named parameters as a dictionary via ‘params’.

hamiltonian(i, j, *args, params=None)

Return the hamiltonian matrix element for sites i and j.

If i == j, return the on-site Hamiltonian of site i.

if i != j, return the hopping between site i and j.

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)

Return a submatrix of the system Hamiltonian.

Parameters

argstuple, defaults to empty

Positional arguments to pass to the hamiltonian method. Mutually exclusive with ‘params’.

to_sitessequence of sites or None (default)

from_sitessequence of sites or None (default)

sparsebool

Whether to return a sparse or a dense matrix. Defaults to False.

return_norbbool

Whether to return arrays of numbers of orbitals. Defaults to False.

paramsdict, optional

Dictionary of parameter names and their values. Mutually exclusive with ‘args’.

Returns

hamiltonian_partnumpy.ndarray or scipy.sparse.coo_matrix

Submatrix of Hamiltonian of the system.

to_norbarray of integers

Numbers of orbitals on each site in to_sites. Only returned when return_norb is true.

from_norbarray 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 to to_sites. The default for from_sites and to_sites is None which means to use all sites of the system in the order in which they appear.

pos(i)

precalculate(energy=0, args=(), leads=None, what='modes', *, params=None)

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

energyfloat

Energy at which the modes or self-energies have to be evaluated.

argssequence

Additional parameters required for calculating the Hamiltionians. Deprecated in favor of ‘params’ (and mutually exclusive with it).

leadssequence 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’.

paramsdict, optional

Dictionary of parameter names and their values. Mutually exclusive with ‘args’.

Returns

systFiniteSystem

A copy of the original system with some leads precalculated.

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)

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’.