Theoretical approaches to one-dimensional and quasi-one-dimensional quantum rings with
a few electrons are reviewed. Discrete Hubbard-type models and continuum models are …

We discuss a state of an orbital glass which may exist in granular superconductors. The
orbital glass is related to the existence of the special loops of Josephson junctions with …

The persistent current in microscopic and mesoscopic Hubbard rings threaded with
magnetic flux is studied as a function of the flux and the Coulomb repulsion parameter U. For …

The ground state of the one-dimensional Kondo lattice model is examined in the strong-
coupling regime. An effective Hamiltonian is developed to describe low-energy processes …

We have studied the energy states and the optical-absorption spectra for interacting
electrons in a quantum ring with the spin degrees of freedom included. We observe features …

The Hubbard model with an additional bond-charge interaction X is solved exactly in one
dimension for the case t= X, where t is the hopping amplitude. In this case the number of …

The persistent current in small isolated rings enclosing magnetic flux is the current
circulating in equilibrium in the absence of an external excitation. While initially studied in …

We study the persistent current in a system of SU ($ N $) fermions with repulsive interaction
confined in a ring-shaped potential and pierced by an effective magnetic flux. By applying a …

The general expression for the persistent current of one-dimensional noninteracting
electrons in a disorder potential with smooth scattering data is derived for zero temperature …

The persistent current in isolated mesoscopic rings is studied using the continuum and tight-
binding models of independent electrons. The calculation is performed with disorder and …