MAGNETIC-FIELD AND CHEMICAL-POTENTIAL EFFECTS ON THE LOW-ENERGY SEPARATION OF THE HUBBARD CHAIN

摘要

We show that in the presence of a magnetic field the usual low-energy separation of the Hubbard chain is replaced by a c and s separation. Here c and s refer to small-momentum and low-energy independent excitation modes which couple both to charge and spin. Importantly, we find the exact generators of these excitations in both the electronic and pseudoparticle bases, In the limit of zero magnetic field these generators become the usual charge and spin fluctuation operators. The c and s elementary excitations are associated with the c and s pseudoparticles, respectively. We also study the separate pseudoparticle left and right conservation laws. In the presence of the magnetic held the small-momentum and low-energy excitations can be bosonized. However, the suitable bosonization corresponds to the c and s pseudoparticle modes and not to the usual charge and spin fluctuations. We evaluate exactly the commutator between the electronic-density operators. Its spin-dependent factor is in general nondiagonal and depends on the interaction. The associate bosonic commutation relations characterize the present unconventional low-energy separation. [References: 35]