Seminar ÚFKL: Juraj Rusnačko

Department of Condensed Matter Physics (ÚFKL) invites you to the lecture

Juraj Rusnačko:
Symmetries of the extended Kitaev model for relativistic transition-metal oxides

The field of Kitaev materials has been a very lively research area for a second decade now. The focal point of interest is how the hallmarks of Kitaev coupling -- quantum spin liquid ground state and bond-directional interactions -- arise in real materials through a subtle interplay of correlations and relativistic effects [1]. The most widely applied minimal model is the extended Kitaev-Heisenberg model that is expected to be relevant for a large group of 3d, 4d and 5d transition metal compounds [2]. In this talk I will present a relatively non-standard methodology of analyzing this model based on its symmetries [3]. First, I will discuss how sublattice-dependent rotations uncover hidden points of SU(2) symmetry in the model. Second, I will show how a surprising cancellation of quantum fluctuations may arise in the bond-directional setting, leading to a continuous manifold of Ising-like classical states. Last, using a simple coordinate transformation, I will present a link to the continuum of single-axis "tripod" models. The talk will also detail how the symmetry analysis may aid in the construction of phasee diagrams or interpretation of experimental excitation spectra.

[1] G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009).
[2] S. M. Winter et al., J. Phys. Condens. Matter 29, 493002 (2017).
[3] J. Rusnačko, D. Gotfryd, and J. Chaloupka, Phys. Rev. B 99, 064425 (2019).