hubbard

◼ hubbard[c] returns the local (Hubbard) electron-electron repulsion operator for the level described by the operator c.
◼ isozsq[c] returns the z-component of the on-site isospin operator squared. This term appears in the expression for electron-electron repulsion in the Anderon model.

◼ Operator c must be expressed in the stripped form, i.e. a form which excludes the first index (creation/annihilation) and the last index (spin).

◼ See also: isozsq, number, pow, chargecharge.

Further examples

Load sneg and declare c to be a fermionic operator

<< sneg`sneg`;
snegfermionoperators[c];

Verify the definition

H = hubbard[c[]]
H == nc[number[c[], CR], number[c[], AN]]

Relation with chargecharge and isozsq

chargecharge[c[], c[]] == 
      number[c[]] + 2 hubbard[c[]]
isozsq[c[]] == 1 - number[c[]] + 2  hubbard[c[]]