CouplingTerms

full name: tenpy.networks.terms.CouplingTerms
parent module: tenpy.networks.terms
type: class

Inheritance Diagram

Methods

`CouplingTerms.__init__`(L)
`CouplingTerms.add_coupling_term`(strength, i, ...)	Add a two-site coupling term on given MPS sites.
`CouplingTerms.add_to_graph`(graph)	Add terms from `coupling_terms` to an MPOGraph.
`CouplingTerms.coupling_term_handle_JW`(...[, ...])	Helping function to call before `add_coupling_term()`.
`CouplingTerms.from_hdf5`(hdf5_loader, h5gr, ...)	Load instance from a HDF5 file.
`CouplingTerms.max_range`()	Determine the maximal range in `coupling_terms`.
`CouplingTerms.plot_coupling_terms`(ax, lat[, ...])	Plot coupling terms into a given lattice.
`CouplingTerms.remove_zeros`([tol_zero])	Remove entries close to 0 from `coupling_terms`.
`CouplingTerms.save_hdf5`(hdf5_saver, h5gr, ...)	Export self into a HDF5 file.
`CouplingTerms.to_TermList`()	Convert `onsite_terms` into a `TermList`.
`CouplingTerms.to_nn_bond_Arrays`(sites)	Convert the `coupling_terms` into Arrays on nearest neighbor bonds.

class tenpy.networks.terms.CouplingTerms(L)[source]

Bases: Hdf5Exportable

Operator names, site indices and strengths representing two-site coupling terms.

Parameters:: L (int) – Number of sites.

L

Number of sites.

Type:: int

coupling_terms

Filled by add_coupling_term(). Nested dictionaries of the form {i: {('opname_i', 'opname_string'): {j: {'opname_j': strength}}}}. Note that always i < j, but entries with j >= L are allowed for bc_MPS == 'infinite', in which case they indicate couplings between different iMPS unit cells.

Type:: dict of dict

max_range()[source]

Determine the maximal range in coupling_terms.

Returns:: max_range – The maximum of j - i for the i, j occurring in a term of coupling_terms.
Return type:: int

add_coupling_term(strength, i, j, op_i, op_j, op_string='Id')[source]

Add a two-site coupling term on given MPS sites.

Parameters:

strength (float) – The strength of the coupling term.
i (int) – The MPS indices of the two sites on which the operator acts. We require 0 <= i < N_sites and i < j, i.e., op_i acts “left” of op_j. If j >= N_sites, it indicates couplings between unit cells of an infinite MPS.
j (int) – The MPS indices of the two sites on which the operator acts. We require 0 <= i < N_sites and i < j, i.e., op_i acts “left” of op_j. If j >= N_sites, it indicates couplings between unit cells of an infinite MPS.
op1 (str) – Names of the involved operators.
op2 (str) – Names of the involved operators.
op_string (str) – The operator to be inserted between i and j.

coupling_term_handle_JW(strength, term, sites, op_string=None)[source]

Helping function to call before add_coupling_term().

Parameters:

strength (float) – The strength of the coupling term.
term ([(str, int), (str, int)]) – List of two tuples [(op_i, i), (op_j, j)] where i is the MPS index of the site the operator named op_i acts on; we require i < j.
sites (list of Site) – Defines the local Hilbert space for each site. Used to check whether the operators need Jordan-Wigner strings.
op_string (None | str) –
Operator name to be used as operator string between the operators, or None if the Jordan Wigner string should be figured out.

Warning

None figures out for each segment between the operators, whether a Jordan-Wigner string is needed. This is different from a plain 'JW', which just applies a string on each segment!

Returns:

Arguments for MultiCouplingTerms.add_multi_coupling_term() such that the added term corresponds to the parameters of this function.

Return type:

strength, i, j, op_i, op_j, op_string

plot_coupling_terms(ax, lat, style_map='default', common_style={'linestyle': '--'}, text=None, text_pos=0.4)[source]

Plot coupling terms into a given lattice.

This function plots the coupling_terms

Parameters:

ax (matplotlib.axes.Axes) – The axes on which we should plot.
lat (Lattice) – The lattice for plotting the couplings, most probably the M.lat of the corresponding model M, see lat.
style_map (function | None) – Function which get’s called with arguments i, j, op_i, op_string, op_j, strength for each two-site coupling and should return a keyword-dictionary with the desired plot-style for this coupling. By default (None), the linewidth is given by the absolute value of strength, and the linecolor depends on the phase of strength (using the hsv colormap).
common_style (dict) – Common style, which overwrites values of the dictionary returned by style_map. A 'label' is only used for the first plotted line.
text (format_string | None) – If not None, we add text labeling the couplings in the plot. Available keywords are i, j, op_i, op_string, op_j, strength as well as strength_abs, strength_angle, strength_real.
text_pos (float) – Specify where to put the text on the line between i (0.0) and j (1.0), e.g. 0.5 is exactly in the middle between i and j.