Magnetic Weyl-Kondo semimetals induced by quantum fluctuations

Weyl-Kondo semimetals are strongly correlated topological semimetals that develop through the cooperation of the Kondo effect with space group symmetries. The Kondo effect, capturing quantum fluctuations associated with strong correlations, is usually suppressed by magnetic order. Here we develop the theory of magnetic Weyl-Kondo semimetal. The key of the proposed mechanism is that the magnetic order comes from conduction $d$ electrons, such that the local $f$ moments can still fluctuate. We illustrate the extreme case where the magnetic space group symmetries prevent any spontaneous magnetization on the sites with the $f$-orbitals. In this case, topological degeneracies, including hourglass Weyl-Kondo nodal lines, appear when the magnetic space group symmetry constrains the Kondo-driven low-energy excitations; they lead to a third-order nonlinear anomalous Hall response. Based on the proposed mechanism, we explore the interplay between strong correlations and symmetries with database search leading to several candidate materials. The most prominent candidates are antiferromagnetic $\rm UNiGa$ and $\rm UNiAl$, with a third-order anomalous Hall response, as well as ferromagnetic $\rm USbTe$ and $\rm CeCoPO$, with a first-order one. Our findings pave the way for future experimental and theoretical investigations that promise to further advance the overarching theme of strongly correlated topology.