Raman studies in Kagome lattices

Abstract:

Kagome pattern belongs to the eleven Archimedian lattices that are characterized by equidistant nodes and allow one to regularly tile a plane. The Kagome lattice combines hexagons and triangles entailing an electronic band structure similar to that of graphene displaying Dirac and occasionally Weyl points. In contrast to graphene, these specific intersection points of the bands are away from the Fermi surface. If atoms with magnetic moments sit on the lattice nodes various types of magnetism are observed including ordered ground states, frustration, and spin liquids. In addition, density waves and superconductivity may occur. Light scattering experiments can access most of these phenomena either directly or indirectly via the phonons. Currently, we (the experimentalists in general and community of light scatterers in particular) are far from having a clear picture of the various ordering phenomena but some of the features become more transparent now. I will focus on Fe₃Sn₂ and CsV₃Sb₅ ordering magnetically and electronically, respectively. In Fe₃Sn₂ one of the phonons is sensitive to the reorientation of the ferromagnetically ordered spins at approximately 100 K. In CsV₃Sb₅ charge-density-wave order is observed exhibiting a large gap, collective modes and phonon anomalies. Due to the low transition temperature of approximately 3 K the superconducting phase is not accessible but the Fano shape of one of the phonon lines suggests a contribution from electron-phonon coupling to Cooper pairing.

Room: REC/C213

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