Topological Kondo semimetals emulated in hetero-bilayer transition metal dichalcogenides

TL;DR

This paper demonstrates that hetero-bilayer transition metal dichalcogenides can emulate topological Kondo semimetals, revealing a tunable platform with emergent flat bands, spontaneous Hall effects, and connections to Weyl Kondo semimetals.

Contribution

It introduces a topological Kondo semimetal phase in MoTe2/WSe2 heterobilayers, combining topology, Kondo physics, and moiré structures for the first time.

Findings

Identification of a Kondo semimetal phase with flat bands

Observation of a spontaneous Hall effect due to inversion symmetry breaking

Prediction of a Berry curvature dodecapole leading to higher-order Hall responses

Abstract

The moir\'{e} structure of AB-stacked $\rm{MoTe_2/WSe_2}$ represents a natural platform to realize Kondo lattice models, due to the discrepancy of the bandwidth between the individual layers. Here, we study this system at the commensurate filling of $\nu_{\rm tot}=2$. Our focus is on the $1+1$ filling setting of $\nu_{\rm Mo} =\nu_{\rm W}=1$, which enables a Kondo lattice description. We find a Kondo semimetal due to the sizable intra-orbital hopping among the electrons in the $\rm{MoTe_2}$ layer. The Kondo-driven (emergent) flat band is naturally pinned to the Fermi energy. When combined with the inherent topology of the electronic structure, a topological Kondo semimetal phase ensues. We calculate the valley Hall response and, due to the breaking of inversion symmetry, also identify a spontaneous Hall effect. There is a Berry curvature dodecapole, which leads to a fourth-order spontaneous Hall effect in the perturbative regime of the electric field that is further amplified in the non-perturbative regime. As such, the system provides a tunable setting to simulate topological Kondo semimetals. Finally, we discuss the pathways that connect the physics realized here to the Weyl Kondo semimetals and their proximate phases that have been advanced in recent years in topological Kondo lattice models and materials.