Search results for "Jahn–Teller effect"
showing 5 items of 25 documents
Electron-hole bilayer quantum dots: Phase diagram and exciton localization
2003
We studied a vertical ``quantum dot molecule'', where one of the dots is occupied with electrons and the other with holes. We find that different phases occur in the ground state, depending on the carrier density and the interdot distance. When the system is dominated by shell structure, orbital degeneracies can be removed either by Hund's rule, or by Jahn-Teller deformation. Both mechanisms can lead to a maximum of the addition energy at mid-shell. At low densities and large interdot distances, bound electron-hole pairs are formed.
A symmetry adapted approach to the dynamic Jahn-Teller problem: Application to mixed-valence polyoxometalate clusters with keggin structure
2012
In this article, we present a symmetry-adapted approach aimed to the accurate solution of the dynamic vibronic problem in large scale Jahn-Teller (JT) systems. The algorithm for the solution of the eigen-problem takes full advantage of the point symmetry arguments. The system under consideration is supposed to consist of a set of electronic levels mixed by the active JT and pseudo JT vibrational modes. Applying the successive coupling of the bosonic creation operators, we introduce the irreducible tensors that are called multivibronic operators. Action of the irreducible multivibronic operators on the vacuum state creates the vibrational symmetry adapted basis that is subjected to the Gram-…
A high-temperature x-ray absorption spectroscopy study of
1996
We present for the first time a high-temperature x-ray absorption spectroscopy study of at the edge. The analysis both of the XANES and of the EXAFS regions shows that, in , a progressive localization of the 5d states following the temperature rise is accompanied at T > 350 K by a distortion of the octahedra, which increases up to the decomposition temperature . The distortion leads to the lowering of the rhenium site symmetry from and is due to the electron - phonon coupling of the 5d electrons with the and phonons and to the Jahn - Teller effect caused by the rhenium electron which becomes localized at high temperature.
Jahn-Teller distortion aroundFe4+inSr(FexTi1−x)O3−δfrom x-ray absorption spectroscopy, x-ray diffraction, and vibrational spectroscopy
2007
$\mathrm{Sr}({\mathrm{Fe}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ perovskites (strontium titanate ferrite solid solution) with well-defined oxygen stoichiometry have been studied as a function of iron concentration by x-ray diffraction, Fe and Ti $K$-edge x-ray absorption spectroscopy (XAS), and vibrational (Raman and infrared) spectroscopy. In reduced $\mathrm{Sr}({\mathrm{Fe}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3\ensuremath{-}x∕2}$ samples, the analysis of the Fe $K$-edge extended x-ray absorption fine structure indicates the expected presence of oxygen vacancies ${\mathrm{V}}_{\mathrm{O}}^{∙∙}$ in the first coordination shell…
Jahn–Teller effects in Au25(SR)18
2016
The relationship between oxidation state, structure, and magnetism in many molecules is well described by first-order Jahn–Teller distortions. This relationship is not yet well defined for ligated nanoclusters and nanoparticles, especially the nano-technologically relevant gold-thiolate protected metal clusters. Here we interrogate the relationships between structure, magnetism, and oxidation state for the three stable oxidation states, −1, 0 and +1 of the thiolate protected nanocluster Au25(SR)18. We present the single crystal X-ray structures of the previously undetermined charge state Au25(SR)18+1, as well as a higher quality single crystal structure of the neutral compound Au25(SR)180. …