Fluorescence decay times measured in the S1 and Sz emission regions are reported for a number of aromatic hydrocarbons in the vapour phase at low pressures. In contrast to the theory which applies to the intermediate strong coupling case, the decay times of the S2 emission are significantly shorter
Characterization of the ground states of a simplified CuO2 model in strong- and weak-coupling regions
β Scribed by Masao Ogata; Hiroyuki Shiba
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- English
- Weight
- 794 KB
- Volume
- 158
- Category
- Article
- ISSN
- 0921-4534
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β¦ Synopsis
The ground states of small clusters are studied within a simplified model for the two-dimensional CuO2 plane, in which doped holes on oxygen p orbitals couple with localized Cu spins. Three cases are found where the ground state has different symmetry from each other: (i) strong ferromagnetic coupling region, (ii) relatively weak coupling region, and (iii) strong antiferromagnetic coupling region. This shows that the strong coupling region is not connected smoothly to the weak coupling region, reminding us of a similar situation in the two-impurity Kondo problem. Local characters of doped holes as well as the nature of the groundstate wave function are investigated to clarify differences among these cases. The strong antiferromagnetic coupling is found to be the most favorable for pairing with short coherence length owing to quantum-mechanical mixing.
π SIMILAR VOLUMES
Real and imaginary part of the self energy and the density of states are calculated in second order parhaily self consistent Green's functmn expansion. There appear upper and lower Hubbard bands and correlation states at the chemical potential.