Far-infrared absorption of a confined two-dimensional electron gas with an imbedded Coulomb impurity

Guðmundsson, Viðar; Loftsdottir, Agusta

doi:10.1103/physrevb.50.17433

Cited by 12 publications

(15 citation statements)

References 22 publications

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“…4,5 In spite of the lacking of experimental information, the study of nanoscopic ring structures has already attracted a strong theoretical interest. [6][7][8][9][10][11] We recall that due to the nonapplicability of the generalized Kohn theorem, a very rich spectroscopic structure is expected to appear in few electrons nanorings, as anticipated by Halonen, Pietiläinen, and Chakraborty 9 and also found in recent works. …”

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confidence: 64%

Far-infrared spectroscopy of nanoscopic InAs rings

et al. 2000

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We have employed time-dependent local-spin-density theory to analyze the far-infrared transmission spectrum of InAs self-assembled nanoscopic rings recently reported ͓A. Lorke et al., Phys. Rev. Lett. ͑to be published͔͒. The overall agreement between theory and experiment is fairly good, which on the one hand confirms that the experimental peaks indeed reflect the ringlike structure of the sample, and on the other hand, asseses the suitability of the theoretical method to describe such nanostructures. The addition energies of oneand two-electron rings are also reported and compared with the corresponding capacitance spectra. Recent progress in nanofabrication techniques1,2 has allowed us to construct self-assembled nanoscopic InGaAs quantum rings occupied with one or two electrons each, and submitted to perpendicular magnetic fields ͑B͒ of up to 12 T. These are spectroscopic data available on rings in the scatterfree, few electrons limit in which quantum effects are best manifested. Previous spectroscopic studies dealt with microscopic rings 3 in GaAs-Ga x Al 1Ϫx As heterostructures, fairly well reproduced by classical or hydrodynamical models. 4,5 In spite of the lacking of experimental information, the study of nanoscopic ring structures has already attracted a strong theoretical interest. [6][7][8][9][10][11] We recall that due to the nonapplicability of the generalized Kohn theorem, a very rich spectroscopic structure is expected to appear in few electrons nanorings, as anticipated by Halonen, Pietiläinen, and Chakraborty 9 and also found in recent works. 12,13In this paper we attempt a quantitative description of some spectroscopic and ground-state (gs) properties of the experimentally studied nanoscopic rings 1,2 using currentdensity ͑CDFT͒ and time-dependent local-spin-density ͑TDLSDFT͒ functional theories. The reason for such an attempt is twofold: on the one hand, to contribute to put on a firm basis the interpretation of current experiments as manifestation of actual properties of few-electrons ring-shaped nanostructures; on the other hand, although in principle exact results could be obtained for one and two electron rings using, e.g., exact-diagonalization methods, 8,9 the present one can also be applied to many electron systems, 12 and we think it is worthwhile to explore the capabilities and limitations of density-functional methods to describe such small rings.Following Ref. 6, we have modeled the ring confining potential by a parabola,with 2 R 0 ϭ 14 nm and the frequency 0 fixed to reproduce the high-energy peak found in the far-infrared ͑FIR͒ transmission spectrum at Bϭ0. For Nϭ2 electrons this yields 0 ϳ12.3 meV. The electron effective mass m*ϭ0.063 ͑we write mϭm*m e with m e being the physical electron mass͒ and effective gyromagnetic factor g*ϭϪ0.43 have been taken from the experiments, [14][15][16] and the value of the dielectric constant has been taken to be ⑀ϭ12.4.To obtain the structure of the GS we have resorted to CDFT as described in Refs. 17 and 18, and to obtain the FIR absorption we...

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confidence: 64%

Far-infrared spectroscopy of nanoscopic InAs rings

et al. 2000

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“…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.…”

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confidence: 99%

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

et al. 2001

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We present a systematic study of ground state and spectroscopic properties of many-electron nanoscopic quantum rings. Addition energies at zero magnetic field ͑B͒ and electrochemical potentials as a function of B are given for a ring hosting up to 24 electrons. We find discontinuities in the excitation energies of multipole spin and charge density modes, and a coupling between the charge and spin density responses that allow to identify the formation of ferromagnetic ground states in narrow magnetic field regions. These effects can be observed in Raman experiments, and are related to the fractional Aharonov-Bohm oscillations of the energy and of the persistent current in the ring.

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“…Plasmon modes in very narrow rings have been described within a Hartree plus random-phase approximation, 12 and the charge-density response of a dot with a repulsive impurity in its center has also been worked out. 13 The optical absorption and inelastic scattering of a two-electron quantum ring of a rather large radius ͑480 nm͒ and width ͑20 nm͒ has been discussed in detail, 14 and singleelectron properties of quantum rings with parabolic confinement have been discussed, 15 with the aim of determining the effect of electron-electron interactions on the energy spectrum and magnetic moment associated with the persistent current in a quantum ring. 16 The far-infrared ͑FIR͒ charge-density excitation ͑CDE͒ appears to depend on the ring width.…”

Section: Introductionmentioning

confidence: 99%

Density-functional calculations of magnetoplasmons in quantum rings

et al. 1999

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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

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Far-infrared absorption of a confined two-dimensional electron gas with an imbedded Coulomb impurity

Cited by 12 publications

References 22 publications

Far-infrared spectroscopy of nanoscopic InAs rings

Far-infrared spectroscopy of nanoscopic InAs rings

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

Density-functional calculations of magnetoplasmons in quantum rings

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