triqs.operators.util.observables.S_op

triqs.operators.util.observables.S_op(component, spin_names, orb_names, off_diag=None, map_operator_structure=None)[source]

Create a component of the spin vector operator.

\[\hat S_{x,y,z} = \frac{1}{2}\sum_{i\sigma\sigma'} a^\dagger_{i\sigma} \mathbf{\tau}^{x,y,z}_{\sigma\sigma'} a_{i\sigma'}, \quad\hat S_\pm = \hat S_x \pm i \hat S_y.\]
Parameters:
  • component (string) – Component to be created, one of ‘x’, ‘y’, ‘z’, ‘+’, or ‘-‘.

  • spin_names (list of strings) – Names of the spins, e.g. [‘up’,’down’].

  • orb_names (list of strings or int) – Names of the orbitals, e.g. [0,1,2] or [‘t2g’,’eg’].

  • off_diag (boolean) – Do we have (orbital) off-diagonal elements? If yes, the operators and blocks are denoted by (‘spin’, ‘orbital’), otherwise by (‘spin_orbital’,0).

  • map_operator_structure (dict) – Mapping of names of GF blocks names from one convention to another, e.g. {(‘up’, 0): (‘up_0’, 0), (‘down’, 0): (‘down_0’,0)}. If provided, the operators and blocks are denoted by the mapping of ('spin', 'orbital').

Returns:

S – The component of the spin vector operator.

Return type:

Operator