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Dirac-Kondo semimetals and topological Kondo insulators in the dilute carrier limit

Heavy fermion systems contain not only strong electron correlations, which promote a rich set of quantum phases, but also a large spin-orbit coupling, which tends to endow the electronic states a topological character. Kondo insulators are understood in terms of a lattice of local moments coupled to conduction electrons in a half-filled band, i.e., with a dense population of about one electron per unit cell. Here, we propose that a new class of Kondo insulator arises when the conduction-electron band is nearly empty ( or, equivalently, full ) . We demonstrated the effect through a honeycomb Anderson lattice model. In the empty carrier limit, spin-orbit coupling produces a gap in the hybridized heavy fermion band, thereby generating a topological Kondo insulator. This state can be understood in terms of a nearby phase in the overall phase diagram, a Dirac-Kondo semimetal whose quasiparticle excitations exhibit a non-trivial Berry phase. Our results point to the dilute carrier limit of the heavy-fermion systems as a new setting to study strongly correlated insulating and topological states.