4f crystal field ground state of the strongly correlated topological insulator SmB6

Invited

Abstract

It was recently proposed that the intermediate valent Kondo insulator SmB6 [1,2] is a topological insulator. The proposal is appealing since rare earth Kondo insulators have the necessary ingredients for strong spin-orbit coupling and electrons of opposite parity (4f and 5d). The surface topology depends directly on the symmetries of the bulk states involved. Knowledge about the crystal electric field ground state is therefore crucial. For example, theoretical predictions for the spin texture of the sought-after topological surface states differ for the 4f5 J5/2 ground state configuration being the G8 quartet or the G7 doublet: e.g. the winding direction is opposite [3-6].

We performed bulk-sensitive, core-level non-resonant inelastic hard-x ray scattering (NIXS) measurements that target specifically the ground state symmetry of SmB6. Here we make use of the highly excitonic character of the higher multipole transitions made possible by the large momentum transfer q in our experiment and of the strong directional dependence of the scattering function S(q,w) [7-9], giving the symmetry information of the ground state wave function, even for cubic compounds. We found from our spectra that the G8 quartet governs the ground state symmetry and hence the topological properties of SmB6 [10]. Our experimental results contradict the predictions of band structure calculations [11].

References:
[1] M. Dzero et al., PRL 104, 106408 (2010)
[2] T. Takimoto, J. Phys. Soc. Jpn. 80, 123710 (2011)
[3] P. P. Baruselli and M. Vojta, PRL 115, 156404 (2015)
[4] M. Legner et al., PRL 115, 156405 (2015)
[5] P. P. Baruselli and M. Vojta, PRB 93, 195117 (2016)
[6] N. Xu et al., Nat. Commun. 5, 4566 (2014)
[7] T. Willers, L.H. Tjeng et al., PRL109, 046401 (2012)
[8] M. Sundermann, L.H. Tjeng et al., Sci. Rep. 5, 17937 (2015)
[9] M. Sundermann, L.H. Tjeng et al., PNAS 113, 13989 (2016)
[10] M. Sundermann, L.H. Tjeng et al., arXiv: 1706.08072
[11] C.-J. Kang et al., J. Phys. Soc. Jpn 84, 024722 (2015)

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Presenters

  • Liu Tjeng

    Max Planck Institutes, Max-Planck Institute for Chemical Physics of Solids, Max Planck Institute for Chemical Physics of Solids, Max Planck Institute f. Chemical Physics of Solids, Dresden

Authors

  • Liu Tjeng

    Max Planck Institutes, Max-Planck Institute for Chemical Physics of Solids, Max Planck Institute for Chemical Physics of Solids, Max Planck Institute f. Chemical Physics of Solids, Dresden

  • Martin Sundermann

    Institute of Physics II, University of Cologne, Institute of Physics II, University of Cologne, Cologne

  • Hasan Yavas

    PETRA III, Deutsches Elektronen-Synchrotron DESY, Hamburg

  • Kai Chen

    Department of Physics, University of Arizona, Institute of Physics II, University of Cologne, Cologne

  • D.J. Kim

    Department of Physics and Astronomy, University of California - Irvine, Department of Physics and Astronomy, University of California, Irvine

  • Zachary Fisk

    Physics and Astronomy, University of California, Department of Physics and Astronomy, Univ of California - Irvine, Department of Physics and Astronomy, University of California - Irvine, University of California Irvine, University of California, Irvine, Physics, University of California, Los Alamos National Laboratory, Department of Physics, University of California, Physics, University of California, Irvine, Department of Physics and Astronomy, University of California, Irvine

  • Deepa Kasinathan

    Max Planck Institute for Chemical Physics of Solids, Max Planck Institute f. Chemical Physics of Solids, Dresden

  • Maurits Haverkort

    Institute for Theoretical Physics, Heidelberg University, Heidelberg

  • Peter Thalmeier

    Max Planck Institute f. Chemical Physics of Solids, Dresden

  • Andrea Severing

    Institute of Physics II, University of Cologne, Institute of Physics II, University of Cologne, Cologne