Weyl-Kondo Semimetal in Heavy Fermion Systems

The study of strongly correlated and topologically nontrivial insulators goes back in decades to quantum Hall systems. By contrast, topological conductors with strong correlations have yet to be identified. Heavy fermion semimetals are a prototype of strongly correlated systems and, given their inherently strong spin-orbit coupling, present a natural setting to make progress. We have advanced a Weyl-Kondo semimetal phase [1] within a well-defined three-dimensional lattice model that breaks the inversion symmetry. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. This has allowed us to propose a key thermodynamic signature of the Weyl-Kondo semimetal phase, viz. the specific heat C going as T cubed with a prefactor enhanced by as much as 9 orders of magnitude compared to the expected value for weakly correlated systems. This thermodynamic signature has been realized in the recently discovered heavy fermion semimetal Ce₃Bi₄Pd₃ [2]. Our findings provide the much-needed theoretical foundation for the experimental search of topological conductors with strong correlations, and open up a way for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom.
[1] H.-H. Lai, S. E. Grefe, S. Paschen, and Q. Si, arXiv:1612.03899 (2016).
[2] S. Dzsaber et al., Phys. Rev. Lett. 118, 246601 (2017).