M. Manninen

Quantum rings for beginners: energy spectra and persistent currents

Abstract 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 shown to give similar results governed by the special features of the one-dimensionality. The energy spectrum of the many-body states can be described by a rotation–vibration spectrum of a “Wigner molecule” of “localized” electrons, combined with the spin-state determined from an effective antiferromagnetic Heisenberg Hamiltonian. The persistent current as a function of the magnetic flux through the ring shows periodic oscillations arising from the “rigid rotation” of the electron ring. For polarized electrons the periodicity of the oscillations is always the flux quantum Φ 0 . For nonpolarized electrons the periodicity depends on the strength of the effective Heisenberg coupling and changes from Φ 0 first to Φ 0 /2 and eventually to Φ 0 / N when the ring gets narrower.

Density functional study of alkali-metal atoms and monolayers on graphite (0001)

Alkali-metal atoms (Li, Na, K, Rb, Cs), dimers, and

Heat transport in ultrathin dielectric membranes and bridges

(2\ifmmode\times\else\texttimes\fi{}2)

Formation of Wigner molecules in small quantum dots

monolayers on a graphite (0001) surface have been studied using density functional theory, pseudopotentials, and a periodic substrate. The adatoms bind at the hollow site (graphite hexagon), with Li lying closest to

Melting and evaporation of argon clusters

(1.84\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})

Quantum Dots in Magnetic Fields: Phase Diagram and Broken Symmetry at the Maximum-Density-Droplet Edge

and Cs farthest

Thermal expansion in small metal clusters and its impact on the electric polarizability

(3.75\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})

Trapping of quasiparticles of a nonequilibrium superconductor

from the surface. The adsorption energies range between 0.55 and

Rotational and vibrational spectra of quantum rings

1.21\phantom{\rule{0.3em}{0ex}}\mathrm{eV}

An ab initio study of cluster–surface interaction: Na clusters on the NaCl(001) surface

, and the energy ordering of the alkali-metal adatoms is