Seminář ÚFKL: Andrzej Oleš

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Andrzej M. Oleš (Institute of Theoretical Physics, Jagiellonian University, Kraków, Poland):
Spin-Orbital Entanglement in Mott Insulators

In a Mott insulator spin and orbital operators belong to the same Hilbert space and therefore these operators may be entangled. This is best seen in the onedimensional model in the absence of Hund’s exchange. The phase diagram shows then a perfect spin-orbital symmetry. However, this symmetry is broken by Hund’s exchange and then the superexchange is disentangled as in the Kugel-Khomskii model, where energy may be gained either by spin or by orbital order. Therefore, the superexchange is either ferromagnetic or antiferromagnetic in the ground state, depending on the direction. Excitations are in general entangled as well and this is mostly unexplored. The spin-orbital models with t_2g electrons are even more entangled as seen in cubic vanadium oxides.

It is also possible to join the seminar online using zoom.

This lecture was supported by the project QM4ST (Quantum materials for applications in sustainable
technology), reg. no. CZ.02.01.01/00/22_008/0004572, cofunded by the ERDF from the Programme Johannes
Amos Commenius, call Excellent Research.