Several- and Many-Electron Artificial-Atoms at Filling Factors between 2 and 1

Abstract

An analysis of potassium-like Ni X in the 15-170 nm wavelength region is reported following observations involving collision-based spectroscopy and laser plasma spectroscopy. Forty five transitions from different excited states in Ni X are identified. Twenty new energy levels of Ni X have been established. The analysis was supported by Hartree-Fock calculations, isoelectronic comparison and the consistency of energy differences between transitions from common initial states. Compared to isoelectronic ions of lower Z, the doublet structure in this spectrum is effectively destroyed by 3p 6 5d, 6d + 3p 5 3d4p, 3p 4 3d 3 configuration interaction.

Integer filling factor phases and isospin in vertical diatomic artificial molecules

“…Although by no means featureless, the amplitude of the Coulomb oscillations also fall-off, as is the case for the b = 2.5 nm QM and a single dot. 6,18,19 To the best of our knowledge, no attempt has previously been made to explain even global features of the vertical QM B ʈ − N phase diagrams over a wide range of N and b. While the concept of isospin has often been discussed in the literature, we found that hardly any published model comes close to adequately accounting for the observed properties of our particular real double quantum dot system as summarized in Fig.…”

“…The low-B ʈ border of this phase agrees well with the distinct B = 2 line in the experiment, but the high-B ʈ border, identifying the first spin-flip, is not clear in the data shown, as is also the case for a single vertical QD. 18 As discussed in Sec. II, the phase diagrams noticeably change when the coupling is reduced, and as far as we know, no model exists to explain all the experimental observations.…”

“…The b = 2.5 nm QM phase diagram has striking similarities to that of a single QD, 18 so by studying the pattern of "wiggles" for each Coulomb oscillation, we can identify two threshold lines marking the onset of integer filling factor , phases (regions) labeled B = 2 and B = 1. The former essentially marks the end of the s.p.…”

“…states are occupied, barely visible kinks (weak steps) appear and are related to spin-flips (MDD reconstructions). 6,18 We point out that in addition to identifying the phases from characteristic features of the Coulomb oscillations, we can also identify the GS transitions, particularly at small N, by looking at the evolution with B ʈ of both ground and excited states in the excitation spectra when V d is increased to typically 1 -2 mV (the current oscillations become current stripes). This spectroscopic technique is comprehensively described elsewhere, 21 and has been applied to strongly coupled and intermediately coupled QM's for N Ͻ 7.…”

“…6,11 The phase diagrams for b = 4.7 and 6.0 nm QM's are clearly different from those of the b = 2.5 nm QM and a single QD. 6,18,19 We can say the following: (i) The phase diagrams for these QM's are more complex than the phase diagram for the b = 2.5 nm QM. This is particularly so for the b = 4.7 nm QM, but is expected since it is intermediate be- Nonetheless, for N exceeding ϳ10, we can approximately identify two lines, labeled T = 4 and T =2 (the full meaning of these filling factor terms is given in Sec.…”