Dresden 2026 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 21: Electron Theory of Magnetism and Correlations (joint session MA/TT)
TT 21.9: Vortrag
Montag, 9. März 2026, 17:15–17:30, POT/0151
Ab initio spin Hamiltonians and magnetism of Ce and Yb triangular-lattice compounds — Leonid V. Pourovskii1,2, •Rafael D. Soares3, and Alexander Wietek3 — 1CPHT, CNRS, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France — 2Collège de France, Université PSL, 11 place Marcelin Berthelot, 75005 Paris, France — 3Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany
We calculate the crystal-field splitting, ground-state Kramers doublet and intersite exchange interactions within the ground-state doublet manifold for a representative set of Ce and Yb triangular-lattice compounds. These include the putative quantum spin liquids (QSL) RbCeO2 and YbZn2GaO5 and the antiferromagnets KCeO2 and KCeS2. The calculated nearest-neighbor (NN) couplings are antiferromagnetic and exhibit noticeable anisotropy. The next-nearest-neighbor (NNN) couplings are ferromagnetic in the Ce systems and dominated by classical dipole–dipole interactions in the Yb case. Solving the resulting effective spin-1/2 models by exact diagonalization up to N=36 sites, we predict ordered magnetic ground states for all systems, including the two QSL candidates. We explore the phase space of an anisotropic NN + isotropic NNN triangular-lattice model finding that a significant antiferromagnetic NNN coupling is required to stabilize QSL phases, while the NN exchange anisotropy is detrimental to them. Our findings highlight a possibly important role of deviations from the perfect triangular model in real materials.
Keywords: Quantum Spin Liquids; Dirac Spin Liquid; Exact Diagonalization; First-principles calculations; Rare-earth magnetic materials