Dresden 2026 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

TT: Fachverband Tiefe Temperaturen

TT 26: Correlated Magnetism – Frustrated Systems

TT 26.3: Talk

Tuesday, March 10, 2026, 10:00–10:15, HSZ/0103

Nature of intersite exchange interactions in Ce triangular-lattice delafossites — •Leonid Pourovskii — CPHT, CNRS, Ecole polytechnique, IP Paris, 91120 Palaiseau, France — Collège de France, Université PSL, 75005 Paris, France

Anisotropic intersite exchange interactions (IEI) in frustrated rare-earth magnets are difficult to assess both theoretically and experimentally. We propose an ab initio force-theorem framework combining the quasi-atomic Hubbard-I approach to 4f correlations with a static mean-field treatment of the on-site intershell Coulomb interaction between rare-earth 4f and 5d states to simultaneously capture both 4f superexchange and 5d-mediated indirect exchange. Applying it to a set of Ce delafossites – the selenide CsCeSe₂, sulfide KCeS₂, and oxide RbCeO₂ – we find a remarkable qualitative evolution of IEI. While the superexchange is found to dominate over the indirect exchange in the oxide, the situation is reversed in the selenide. Both coupling mechanisms are found to contribute comparably in the sulfide. The calculated IEI place CsCeSe₂ and KCeS₂ in the yz-stripe region of the published spin-1/2 triangular-lattice model phase diagram, in agreement with experiment, while those for RbCeO₂ correspond to the 120^∘ antiferromagnetic order. The magnetic excitation spectra of CsCeSe₂ and KCeS₂ evaluated from the calculated spin Hamiltonains are in good qualitative and quantitative agreement with experimental data.

Keywords: Exchange interactions; Frustrated magnetism; Rare-earth magnetic materials; Triangular lattice; DMFT