[Seminar] "j=3/2 Quantum Spin-Orbital Liquids" by Mr. Willian Natori

[Speaker]

Mr. Willian Natori - PhD. Candidate, University of São Paulo, Campus of São Carlos

[Abstract]

The search for quantum spin liquids (QSLs) in solid state platforms gained a new focus thanks to the discovery that the Kitaev model could be realistically implemented in heavy transition metal compounds, the so-called Kitaev materials . This seminal work of Jackeli and Khaliullin showed how strong correlations, spin-orbit coupling and lattice constraints lead to effective models with anisotropic and bond-dependent super-exchange interactions favoring exotic magnetic states. In this talk, I present how this mechanism applied to  4/5d¹ ions leads to j=3/2 effective models, which are directly related to Kugel-Khomskii models with doubly degenerate orbitals. I explicit two realistic models describing the magnetism of double perovskites (PRL 117, 017204; PRB 96, 125109) and compounds isostructural to the Kitaev materials (arXiv 1802.00044). Besides the bond-dependent anisotropic interactions like the Kitaev model, the models also show continuous symmetries at certain limits that enhance quantum fluctuations. Using parton theory, I propose fermionic QSLs on them and show how their energetics are evaluated with Variational Monte Carlo Methods. The expected response of the QSL on double perovskites is compared with the experimental data available for the compound Ba₂YMoO₆. I also show how resonant inelastic x-ray scattering can probe dynamical correlations inaccessible for neutron scattering in these compounds. Perspectives for future work are given in the end of this talk.