YRLG Workshop: Correlation and Topology in magnetic materials, July 16th - 18th 2024
Mike Ziebel
Materials combining strongly localized magnetic moments and itinerant electrons can host competition between the RKKY interaction, which favors magnetically ordered ground states, and the Kondo interaction, which favors non-magnetic heavy Fermi liquid ground states. This competition gives rise to rich electronic and magnetic phase diagrams that are highly sensitive to chemical modification, structural distortions, and magnetic frustration. Dimensional reduction, in particular, has proven to be an effective strategy to access the quantum critical regime at the crossover between magnetic and non-magnetic states in these materials, motivating the study of 2D or quasi-2D materials hosting these interactions. In the first part of this talk, I will discuss the discovery of two-dimensional heavy fermions in the van der Waals metal CeSiI. Bulk thermodynamic measurements, paired with scanning tunneling and angle-resolved photoemission spectroscopies, provide evidence for strong electronic correlations in CeSiI, while magnetotransport measurements on bulk and 2D flakes evidence the reduced dimensionality of its electronic structure. At low temperature, CeSiI displays incommensurate antiferromagnetic order driven by a van Hove singularity (vHS) close to the Fermi energy. Paired with the ability to exfoliate CeSiI to few-layer flakes, these properties make CeSiI an ideal platform to study and manipulate Kondo physics at the 2D limit. In the second part of my talk, I will discuss a structurally related family of materials combining cerium with magnetic transition metals. Crystal symmetry and the presence of two magnetic sub-lattices generate complex magnetic structures in these materials with tunable but unconventional anomalous Hall effects. Substitution of cerium with other rare earth metals in these materials provides a route to enhance the magnetic ordering temperature and to further modify the magnetic structure. Collectively, these materials highlight the possibility to engineer magnetism, correlations, and possibly topology, in quasi-2D materials hosting low valent rare earth metals.