ARPES insight into the properties of f-electrons in rare-earth intermetallics RERh_2Si_2 (RE = Ce, Eu, Gd and Yb)

For a long time, rare-earth (RE) intermetallic materials have attracted considerable interest because of their exotic properties at low temperatures which include complex magnetic phases, valence fluctuations, heavy-fermion states, 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 reveal the fine electronic structure of such materials near the Fermi level by means of ARPES. 

In the past years, we performed extensive studies on the RERh_2Si_2 (RE = Ce, Eu, Gd and Yb) series of compounds as well as on YbIr_2Si_2. 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 (YbRh_2Si_2); (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 EuRh_2Si_2 & GdRh_2Si_2 caused by buried 4f magnetic moments of Eu (Gd) 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 Communications 5, 3171 (2014).

[2] M. Höppner et. al., Interplay of Dirac fermions and heavy quasiparticles in solids, Nature Communications 4, 1646 (2013).

[3] S. Danzenbächer et. al., Insight into the f-derived Fermi surface of the heavy-fermion compound YbRh_2Si_2, Phys. Rev. Lett. 107, 267601 (2011).

[4] D.V. Vyalikh et. al., k-dependence of the crystal-field splittings of 4f states in rare-earth systems, Phys. Rev. Lett. 105, 237601 (2010).

[5] D.V. Vyalikh et. al., Tuning the hybridization at the surface of a heavy-fermion system,
Phys. Rev. Lett., 103, 137601 (2009).