Experimental Evidence for Weyl Semimetal Behavior in Kondo Systems*

The quest for topologically nontrivial phases in strongly correlated electron systems has recently led to the notion of Weyl-Kondo semimetals [1]. We have observed direct thermodynamic evidence for the corresponding linear electronic dispersion, with strongly renormalized velocity, in the new non-centrosymmetric cubic material Ce₃Bi₄Pd₃ [2]. Its isostructural sister compound Ce₃Bi₄Pt₃ is a canonical Kondo insulator. Our study of the substitution series Ce₃Bi₄(Pt_1-xPd_x)₃ showed that, while the replacement of the 5d element Pt by the much lighter 4d element Pd strongly reduces the conduction electron spin-orbit coupling, it is isostructural, isoelectronic, and isosize [2]. This indicates that the Weyl semimetal state may develop near a (non-centrosymmetric) Kondo insulator in the presence of reduced spin-orbit coupling. Also other candidate materials, in particular tetragonal CeRu₄Sn₆ [3-5] and orthorhombic CeNiSn [6], will be discussed.
[1] H.-H. Lai, S. E. Grefe, S. Paschen, and Q. Si, arXiv:1612.03899.
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[3] V. Guritanu, P. Wissgott, T. Weig, H. Winkler, J. Sichelschmidt, M. Scheffler, A. Prokofiev, S. Kimura, T. Iizuka, A. M. Strydom, M. Dressel, F. Steglich, K. Held, and S. Paschen, Phys. Rev. B 87, 115129 (2013).
[4] 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, and A. Severing, Sci. Rep. 5, 17937 (2015).
[5] Y. Xu, C. Yue, H. Weng, X. Dai, Phys. Rev. X 7, 011027 (2017).
[6] U. Stockert, P. Sun, N. Oeschler, F. Steglich, T. Takabatake, P. Coleman, and S. Paschen, Phys. Rev. Lett. 117, 216401 (2016).