Unequal on-site interaction effects in the one-dimensional electron system at quarter filling

The one-dimensional antiferromagnetic correlated electron system described by the unusual t-U-J model with alternating on-site interactions at odd (Uo) and even (Ue) sites is studied analytically. At weak coupling, the use of bosonization and renormalization-group techniques helps to obtain ground-state phase diagram. At quarter filling, the unequal on-site repulsion (Ue not equal Uo) causes the occurrence of umklapp processes and the generation of a charge excitation gap. Contrary to the usual case (Ue=Uo), the system is not metallic but insulating. For Ue+Uo<2J, the system is in a spin-gapped phase with charge-density-wave (CDW) instability; for Ue+Uo2J, the system is in a spin-gapless phase characterized by the coexistence of both CDW and spin-density-wave (SDW) instabilities, where the SDW correlation dominates over the CDW one.

Automated summary

The one-dimensional antiferromagnetic correlated electron system described by the unusual t-U-J model with alternating on-site interactions at odd and even sites exhibits insulating behavior due to unequal on-site repulsion. Depending on the value of Ue+Uo in relation to 2J, the system can be in a spin-gapped phase with charge-density-wave instability or a spin-gapless phase with coexisting CDW and SDW instabilities.