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ARPES insight into the dual nature of 4f electrons in rare-earth intremetallics

Lundi 2 février 2015 14:00 - Duree : 1 heure
Lieu : Salle "Remy Lemaire" K 223 (1er étage) bât. K de l’institut Néel/CNRS

Orateur : Denis VYALIKH

For a long time, rare-earth (RE) intermetallic materials have attracted considerable interest because of their exotic properties at low tempe ratures which include complex magnetic phases, valence fluctuation, heavy-fermion state, Kondo behavior and many others. It is widely believed that all of these properties stem from the delicate interplay between almost localized 4f electrons and itinerant valence band states. Our experiments aim to disclose details of this interaction, and to reveal the fine electronic structure of such materials near the Fermi level. To this end, we apply Angle-Resolved Photoemission Spectroscopy (ARPES), which in spite of its surface sensitivity when working in UV mode, allows to gain deep insight not only into the surface electronic structure, but to probe the bulk derived states, too. One aim of our experiments is the proper discrimination of (sub-) surface and bulk related phenomena. In the past years we performed extensive ARPES studies on the RERh2Si2 (RE = Ce, Eu, and Yb) series of compound as well as on YbIr2Si2 With our approach we were able to address some of the topics at the core of strongly correlated 4f electron systems : (i) observation of crystal-electric field (CEF) splitting of the 4f states and their fine dispersion induced by f-d hybridization ; (ii) insight into the Fermi surface and manifestation of its strong 4f character. Disclosing its topology and features reflecting f-d coupling at the surface and bulk of the material. Studying its temperature dependence for a Kondo lattice (YbRh2Si2) ; (iii) clear evidence of the interplay of Dirac fermions and heavy quasi-particles ; (iv) manifestation of unusual and strong ferromagnetism at the Si-terminated surface of an antiferromagnet (EuRh2Si2) caused by buried 4f magnetic moments of Eu lying 4-layers below the surface. [1] A. Chikina et al., Strong ferromagnetism at the surface of an antiferromagnet caused by buried magnetic moments, Nature Comm. 5, 3171 (2014). [2] M. Höppner et al., Interplay of Dirac fermions and heavy quasiparticles in solids, Nature Comm. 4, 1646 (2013). [3] S. Danzenbächer et al., Insight into the f-derived Fermi surface of the heavy-fermion compound YbRh2Si2, Phys. Rev. Lett. 107, 267601 (2011).

Contact : georg.knebel@cea.fr

Discipline évènement : (Physique)
Entité organisatrice : (INAC/SPSMS)
Nature évènement : (Séminaire)
Site de l'évènement : Polygone scientifique

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