Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 6: Quantum Magnets and Molecular Magnets (joint session TT/MA)
TT 6.10: Vortrag
Montag, 12. März 2018, 12:00–12:15, H 3010
Suppression of spin-crossover by dynamic Jahn-Teller effect in C603− — •Dan Liu, Naoya Iwahara, and Liviu Chibotaru — Theory of Nanomaterials Group, University of Leuven, Leuven, Belgium
In conventional spin crossover systems, the vibrational degrees of freedom enhances the entropic effect in excited high-spin terms resulting from the softening of vibrations [1]. Here, we show an opposite effect of vibration on the spin crossover taking C603− as an example [2]. The vibronic states resulting from dynamical Jahn-Teller effect in C603− are obtained using the numerical diagonalization of the linear pn ⊗ 8d Jahn-Teller Hamiltonian with the currently established coupling parameters. It is found that the Jahn-Teller effect stabilizes the low-spin states, resulting in the violation of Hund’s rule. The energy gain due to the Jahn-Teller dynamics is found to be comparable to the static Jahn-Teller stabilization. The Jahn-Teller dynamics influences the thermodynamic properties via strong variation of the density of vibronic states with energy. Thus, the large vibronic entropy in the low-spin states enhances the effective spin gap of C603− quenching the spin crossover. This finding is used for the rationalization of the experimental data on the spin gaps in various fullerides.
[1] P. Gütlich, A. Hauser, and H. Spiering, Angew. Chem. Int. Ed. 33, 2024 (1994).
[2] D. Liu, N. Iwahara, and L. F. Chibotaru, arXiv:1711.00340 [cond-mat.mtrl-sci].