Persistent currents and spin-charge separation in a one-dimensional Hubbard ring with side sites

Abstract

The persistent current and spin-charge separation are studied in a one-dimensional (1D) Hubbard ring with side sites connected to the even sites of the ring. At half filling, the persistent current is always paramagnetic and has a period of flux quantum. Away from half filling, as the onsite repulsion $U$ increases, the sign of the current may oscillate depending on the total number of electrons ${N}_{e}$ and the hopping $t$ between the ring site and the side site. For small hopping $t$, the number of electrons ${N}_{e}^{\ensuremath{'}}$ in the ring sites plays an important role in determining the sign of the current. In contrast to the 1D Hubbard model, a weak or a moderate $U$ can strongly enhance the persistent current while the hopping $t$ always suppresses the current. The study on the transmittance of the ring with two connected leads indicates that in the large $U$ and small $t$ case, the transmittance varies with a period $1∕{N}_{e}^{\ensuremath{'}}$ of a flux quantum, demonstrating a spin-charge separation in this system.