Density-functional calculations of magnetoplasmons in quantum rings

Abstract

We have studied the structure and dipole charge-density response of nanorings as a function of the magnetic field using local-spin-density-functional theory. Two small rings consisting of 12 and 22 electrons confined by a positively charged background are used to represent the cases of narrow and wide rings. The results are qualitatively compared with experimental data existing on microrings and on antidots. A smaller ring containing five electrons is also analyzed to allow for a closer comparison with a recent experiment on a two-electron quantum ring. ͓S0163-1829͑99͒02723-X͔

Quantum rings for beginners: energy spectra and persistent currents

“…Density functional theory has the same problem as quantum Monte Carlo in that the determination of excited states is not straightforward (although timedependent current-spin-density-functional theory can provide some information on excitations [92,93,95]). Consequently, it is not possible to construct the complete excitation spectrum as by using the brute force CI method.…”

Multipole modes and spin features in the Raman spectrum of nanoscopic quantum rings

“…The lower energy (ϩ) peak corresponds to the outer edge mode, the high energy (Ϫ) peak to the bulk mode, and the lower (Ϫ) peak to the inner edge mode. 15,21 Actually, the distinction between edge and bulk modes only makes sense at high enough magnetic fields; in the present case, well developed Landau bands appear at B ϳ5 T, and for lower magnetic fields the charge and spin density spectrum is fairly complex.…”

“…5,6 In nanoscopic rings quantum effects are important and for this reason theoretical studies at a more microscopic level have been undertaken. [7][8][9][10][11][12][13][14][15][16][17][18][19] In some of these calculations a major emphasis has been put on describing the Aharonov-Bohm ͑AB͒ quantum effect which manifests in the presence of an external magnetic field ͑B͒ as the existence of a persistent current, and leads to periodic oscillations in the energy spectrum and the persistent current as a function of B. These AB oscillations have been observed in mesoscopic rings in a GaAlAs/GaAs heterostructure by measuring the conductance across the ring.…”

Ground state and far-infrared absorption of two-electron rings in a magnetic field

“…In fact, mesoscopic rings were produced by Dahl et al and their magnetoplasmon resonances measured for different ring widths [2]. Subsequent theoretical models, using semiclassical methods [3] and density functional theory [4] provided a good interpretation of the measured ring spectra. There also exist approaches based on exact diagonalization methods for very small numbers of electrons which have addressed the so called 'persistent current' [5] and the optical excitations for very narrow rings (approaching the 1d limit) as well as for dots with a repulsive scatterer center [6,7].…”