Valence and orbital states of rare earth Heavy Fermion compounds close to the quantum critical point: Resonant and non-resonant inelastic X-ray scattering investigations.
Final Report Abstract
We have performed NIXS experiments at the Ce N-edge (4d → 4f) on several cerium compounds and also at the U O-edge (5d → 5f) on the hidden order uranium compound URu2Si2. With this we have established NIXS as a new method for determining ground state wave functions with x-rays in a bulk sensitive manner, in higher than twofold rotational symmetries, and in uranium compounds. Especially the latter opens a new field of activities. In most cases the wave functions in intermetallic uranium compounds cannot be determined with neutrons due to the enormous lifetime broadening of the magnetic excitations. With NIXS we now have tool at hand that can provide the desired information. We have learned that the PFY-XAS L-edge experiments are great for resolving f1 and f0 spectral weights due to the reduced life time broadening. It is, for example, very useful for determining changes in the valence as function of temperature. However, we also learned that this method has its limitation when absolute f-occupations are desired. Here we found that HAXPES is the superior tool. We have also performed HAXPES measurements on several, very different cerium compounds and analyzed all data with the same combined configuration interaction and full multiplet calculations. This gives us a nice set of comparable configuration interaction parameters that will serve us for future studies. Note, literature values are hard to compare because the valence band is approximated very differently from group to group. We still aim at measuring CeCoIn5 in the quantum critical and superconducting region once the mK insert is available. The consortium agreement guarantees us privileged access for using this insert.
Publications
- Correlation between the valence state of Ce and magnetic transition in Ce(Ru1−xFex)2Al10 studied by resonant x-ray emission spectroscopy. Phys. Rev. B 89, 125108 (2014)
Y. Zekko, Y. Yamamoto, H. Yamaoka, H. Tajima, T. Nishioka, F. Strigari, A. Severing, J.-F. Lin, N. Hiraoka, H. Ishii, K.-D. Tsuei, and J. Mizuki
(See online at https://doi.org/10.1103/PhysRevB.89.125108) - Absence of orbital rotation in superconducting CeCu2Ge2. Phys. Rev. B. 91, 201108(R) (2015)
J.-P. Rueff, J.M. Ablett, F. Strigari, M. Deppe, M.W. Haverkort, L.H. Tjeng, A. Severing
(See online at https://doi.org/10.1103/PhysRevB.91.201108) - CeRu4Sn6: a strongly correlated material with nontrivial topology. Scientific Reports 5, 17937 (2015)
M. Sundermann, F. Strigari, T. Willers, H. Winkler, A. Prokofiev, J. M. Ablett, J.-P. Rueff, D. Schmitz, E. Weschke, M. Moretti Sala, A. Al-Zein, A. Tanaka, M. W. Haverkort, D. Kasinathan, L. H. Tjeng, S. Paschen, A. Severing
(See online at https://doi.org/10.1038/srep17937) - Quantitative study of valence and configuration interactionparameters of the Kondo semiconductors CeM2Al10(M = Ru, Os andFe) by means of bulk-sensitive hard X-ray photoelectron spectroscopy. J. Electr. Spec. and Rel. Phen. 199, 56 (2015)
F. Strigari, M. Sundermann, Y. Muro, K. Yutani, T. Takabatake, K.-D. Tsuei, Y.F. Liao, A. Tanaka, P. Thalmeier, M.W. Haverkort, L.H. Tjeng, A. Severing
(See online at https://doi.org/10.1016/j.elspec.2015.01.004) - Direct bulk sensitive probe of 5f symmetry in URu2Si2. Proc. Nat. Acad. Sci. 113 (49), 13989 (2016)
M. Sunderman, M. W. Haverkort, S. Agrestini, A. Al-Zein, M. Moretti Sala, Y. Huang, M. Golden, A. de Visser, P. Thalmeier, L. H. Tjeng, A. Severing
(See online at https://doi.org/10.1073/pnas.1612791113) - Quantitative study of the f occupation in CeMIn5 and other cerium compounds with hard x-rays. J. Elec. Spec. and Rel. Phen. 209, 1-8 (2016)
M. Sundermann, F. Strigari, T. Willers, J. Weinen, Y. F. Liao, K.-D. Tsuei, N. Hiraoka, H.Ishii, H. Yamaok, J. Mizuki,Y. Zekko, E. D. Bauer, J. L. Sarrao, J. D. Thompson, P. Lejay, Y. Muro, K. Yutani, T. Takabatake, A. Tanaka, N. Hollmann, L. H. Tjeng, A. Severing
(See online at https://doi.org/10.1016/j.elspec.2016.02.002) - Ce 3p hard x-ray photoelectron spectroscopy study of the topological Kondo insulator CeRu4Sn6. Journal of Phys. Conf. Series 807, 022001 (2017)
M. Sundermann, K. Chen, Y. Utsumi, Y.-H. Wu, K.-D. Tsuei, J. Haenel, A. Prokofiev, S. Paschen, A. Tanaka, L.H. Tjeng, A. Severing
(See online at https://doi.org/10.1088/1742-6596/807/2/022001) - The quartet ground state in CeB6: an inelastic x-ray scattering study. Euro Phys. Lett. 117, 17003 (2017)
M. Sundermann, K. Chen, H. Yavas, Han-Oh Lee, Z. Fisk, M. W. Haverkort, L. H. Tjeng, A.Severing
(See online at https://doi.org/10.1209/0295-5075/117/17003)
