Extreme topological response in a nonmagnetic Weyl-Kondo semimetal

The interplay of topology and strong electron correlations is emerging as a new frontier in quantum science; it is expected to bring forth exotic phases and excitations [1], possibly through enhanced quantum fluctuations [2]. Heavy fermion systems provide an ideal setting to explore this new regime: The Kondo interaction implements extreme correlation strength and representatives with strong spin-orbit coupling exist. We have recently discovered Weyl semimetal behavior in the noncentrosymmetric material Ce₃Bi₄Pd₃ [3,4], a sister compound of the canonical Kondo insulator Ce₃Bi₄Pt₃, concurrently with the theoretical development of such a Kondo-driven phase [5,6]. Ce₃Bi₄Pd₃ has a Kondo temperature of 13 K [3] and remains paramagnetic down to at least 250 mK [4]. Our most striking observation is a giant spontaneous (zero-field) Hall effect, and an associated even-in-field Hall component, which provide direct evidence of Berry curvature singularities in close vicinity of the Fermi level [4]. These characteristics of Weyl physics develop only in the Kondo coherent state, and are thus manifestly correlation driven. The application of large magnetic fields leads to an annihilation of the Weyl nodes at a first critical field, and to the metallization of the system at a second one, featuring quantum criticality [7].

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[2] W. T. Fuhrman et al., arXiv:2007.09460.
[3] S. Dzsaber et al., Phys. Rev. Lett. 118, 246601 (2017).
[4] S. Dzsaber et al., arXiv:1811.02819.
[5] H.-H. Lai et al., PNAS 115, 93 (2018).
[6] S.E. Grefe et al., Phys. Rev. B 101, 075138 (2020).
[7] S. Dzsaber et al., arXiv:1906.01182.