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On the Definition of the Current Operator Application to the Hubbard Model

1973; Wiley; Volume: 58; Issue: 1 Linguagem: Inglês

10.1002/pssb.2220580108

1521-3951

Dario Cabib, T. A. Kaplan,

Quantum and electron transport phenomena

Abstract A disagreement existing in the literature between various calculations of the electrical conductivity in the single‐band Hubbard model is resolved. The error, which occurs in a paper by Monecke, is pointed out and explained to be due to the assumption that the current operator, defined as the commutator of the Hubbard Hamiltonian with the polarization operator, is invariant under the lattice translations. The existence of ambiguity in the definition of a “good” current operator (which is translationally invariant) is pointed out and resolved in a large class of situations.