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TT: Fachverband Tiefe Temperaturen

TT 72: Poster Session: Correlated Electrons

TT 72.31: Poster

Mittwoch, 14. März 2018, 15:00–19:00, Poster B

Excitation spectra of hard-core bosons in strongly spin-orbit coupled Van Vleck-type d⁴ Mott insulators — •Friedemann Aust and Maria Daghofer — Institut für Funktionelle Materie und Quantentechnologien, Universität Stuttgart

In spin-orbit coupled Mott insulators with a t_2g⁴ electron configuration, the interplay of spin-orbit coupling, Hund’s rule and Kugel-Khomskii superexchange can be mapped to an effective singlet-triplet model [1]. For honeycomb or triangular lattice geometries, as found in e.g. delafossite, interactions have a bond selective structure reminiscent of the Kitaev honeycomb model. However, the local degrees of freedom are not given by a spin but by a singlet ground state and low-lying triplet excitations, which can be seen as hard-core bosons.

We discuss this model in the presence of direct exchange in addition to inter-orbital superexchange. Going beyond analytic considerations, we use cluster perturbation theory (CPT) and the variational cluster approximation (VCA), where the hard-core constraint can be taken into account, to obtain magnetic excitation spectra in regimes dominated by Heisenberg, Kitaev, or less symmetric couplings.
G. Khaliullin, Phys. Rev. Lett. 111, 197201 (2013).