momentum_mps

• full name: tenpy.networks.momentum_mps

• parent module: tenpy.networks

• type: module

Classes

MomentumMPS(Xs, uMPS, p[, n_sites])

A Matrix Product State, finite (MPS) or infinite (iMPS).

Module description

This module contains a base class for a Momentum Matrix Product State.

This is an extension of the uniform MPS UniformMPS.

For each unit-cell site of the initial uniform MPS, we define an excitation tensor B. The momentum state with momentum p is then constructed by the infinite sum, where one of the tensors of the uniform MPS is replaced by the excitation tensor:

|                        ...--AL[n-1] -- B[n] -- AR[n+1] -- ...
| \sum_n  \exp{i p n}          |         |        |

The B tensors can possibly act on multiple neighboring sites to include larger excitations. Furthermore, the B is decomposed into:

|           -B- = - VL -- X -
|            |      |

Here, VL is the orthogonal complement of the corresponding AL tensor, such that the state is always orthogonal to the initial uniform MPS. X parametrizes the excited states.