Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 28: Correlated Electrons: Theory 1
TT 28.1: Vortrag
Donnerstag, 8. September 2022, 09:30–09:45, H23
General super-exchange Hamiltonians for magnetic and orbital physics in eg and t2g systems — •Xuejing Zhang1, Erik Koch1,2, and Eva Pavarini1,2 — 1Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany — 2JARA High-Performance Computing, 52062, Aachen, Germany
In strongly-correlated transition-metal oxides, spin- and orbital-ordering or spin- and orbital-liquid phenomena are often studied with low-energy super-exchange Hamiltonians, derived from multi-band Hubbard models in highly symmetric cases and in the basis of pseudo-spin operators. This captures the essence of the Kugel-Khomskii[1] super-exchange mechanism. Recently, via an irreducible-tensor operator representation, we derived the orbital super-exchange Hamiltonian for t2g1 perovskites and successfully used it, in combination with many-body calculations based on dynamical mean-field theory, to explain the orbital physics in these systems. Then, we generalize our method to egn and t2gn systems at arbitrary integer filling n, including both spin and orbital interactions[2,3]. Here, we identified the t2g2 perovskite LaVO3 as a rare case in which orbital-ordering is indeed controlled by the KK super-exchange interaction[4].
[1] K. I. Kugel’ and D. I. Khomskii, Zh. Eksp. Teor. Fiz. 64, 1429 (1973) [Sov. Phys. JETP 37, 725 (1973)]
[2] X. J. Zhang, E. Koch, E. Pavarini, Phys. Rev. B 102, 035113 (2020)
[3] X. J. Zhang, E. Koch, E. Pavarini, Phys. Rev. B 105, 115104 (2022)
[3] X. J. Zhang, E. Koch, and E. Pavarini, Submitted to Phys. Rev. Lett.