Browsing by Author "Geibel, C."
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Item Crystalline electric field of Ce in trigonal symmetry: CeIr3Ge7 as a model case(American Physical Society, 2018) Banda, J.; Rai, B.K.; Rosner, H.; Morosan, E.; Geibel, C.; Brando, M.The crystalline electric field (CEF) of Ce3+ in trigonal symmetry has recently become of some relevance, for instance, in the search of frustrated magnetic systems. Fortunately, it is one of the CEF cases in which a manageable analytic solution can be obtained. Here, we present this solution for the general case, and use this result to determine the CEF scheme of the new compound CeIr3Ge7 with the help of T-dependent susceptibility and isothermal magnetization measurements. The resulting CEF parameters B02=34.4K, B04=0.82K, and B34=67.3K correspond to an exceptionally large CEF splitting of the first and second excited levels, 374 K and 1398 K, and a large mixing between the ∣∣±52⟩ and the ∣∣∓12⟩ states. This indicates a very strong easy plane anisotropy with an unusually small c-axis moment. Using the same general expressions, we show that the properties of the recently reported system CeCd3As3 can also be described by a similar CEF scheme, providing a much simpler explanation for its magnetic properties than the initial proposal. Moreover, a similar strong easy plane anisotropy has also been reported for the two compounds CeAuSn and CePdAl4Ge2, indicating that the CEF scheme elaborated here for CeIr3Ge7 corresponds to an exemplary case for Ce3+ in trigonal symmetry.Item Evolution of the Kondo lattice and non-Fermi liquid excitations in a heavy-fermion metal(Springer Nature, 2018) Seiro, S.; Jiao, L.; Kirchner, S.; Hartmann, S.; Friedemann, S.; Krellner, C.; Geibel, C.; Si, Q.; Steglich, F.; Wirth, S.Strong electron correlations can give rise to extraordinary properties of metals with renormalized Landau quasiparticles. Near a quantum critical point, these quasiparticles can be destroyed and non-Fermi liquid behavior ensues. YbRh2Si2 is a prototypical correlated metal exhibiting the formation of quasiparticle and Kondo lattice coherence, as well as quasiparticle destruction at a field-induced quantum critical point. Here we show how, upon lowering the temperature, Kondo lattice coherence develops at zero field and finally gives way to non-Fermi liquid electronic excitations. By measuring the single-particle excitations through scanning tunneling spectroscopy, we find the Kondo lattice peak displays a non-trivial temperature dependence with a strong increase around 3.3 K. At 0.3 K and with applied magnetic field, the width of this peak is minimized in the quantum critical regime. Our results demonstrate that the lattice Kondo correlations have to be sufficiently developed before quantum criticality can set in.