Comparative study of the Yb-delafossites NaYbCh2 (Ch : O, S, Se) : From critical quantum spin liquids to field-induced magnetic instabilities

Orateur : K. M. RANJITH (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany)

Spin-orbit entanglement brought significant progress to the field of quantum spin liquids (QSLs). Strong spin–orbit coupling (SOC), associated with the rare-earth magnetic ions leads to anisotropic exchange frustration of the moments. The combination of strong SOC and anisotropic exchange interactions promotes Yb-delafossites to ideal candidates for QSLs. The Yb-based delafossites NaYbCh2 (Ch : O, S, and Se) are regarded as unique model system for planar spin-1/2 triangular-lattice magnetism (TLM). Understanding the SOC-driven QSLs is rather challenging and goes far beyond Andersons RVB theory. Bond-dependent exchange frustration and persisting quantum fluctuations melt the predicted long-range 120o magnetic order. The application of moderate magnetic fields induces and stabilizes antiferromagnetic order. The QSL state is separated from the ordered state by a quantum critical regime in the H- T phase diagram which classifies NaYbCh2 (Ch : O, S, and Se) as critical quantum spin liquid. Here, we present a comprehensive study of bulk probes such as specific heat an d magnetization and local probes such as NMR and ESR over a wide range of temperature (0.05-300 K) and magnetic fields (up to 40 T).

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