Topological Kondo semimetal and insulator in AB-stacked heterobilayer transition metal dichalcogenides

TL;DR

This paper predicts that AB-stacked heterobilayers of transition metal dichalcogenides can host topological Kondo semimetal and insulator states, driven by chiral Kondo coupling and tunable by strain, with potential for novel topological phases.

Contribution

It introduces the concept of topological Kondo states in AB-stacked TMD heterobilayers, highlighting the role of chiral Kondo coupling and strain in realizing these phases.

Findings

Topological Kondo semimetal at filling ν=2 with edge modes.

Strain-induced transition to a topological Kondo insulator with quantized spin Hall conductance.

Chiral Kondo coupling favors topological phases in heterobilayers.

Abstract

Recent experiments reported the realization of a heavy Fermi liquid in AB-stacked MoTe$_2$/WSe$_2$ heterobilayers. In this paper we show that the AB-stacked heterobilayer configuration is particularly suited to realize topological Kondo semimetal and topological Kondo insulator ground states at a doping of two holes per moir\'e unit cell. The small lattice mismatch between the MoTe$_2$ and WSe$_2$ monolayers and the different bandwidths of their highest lying moir\'e valence bands means that, in the experimentally relevant range of hole dopings, the MoTe$_2$ layer is effectively a Mott insulator with only low-lying magnetic excitations Kondo-coupled to more itinerant electrons in the WSe$_2$. The crucial consequence of the AB-stacking configuration is that the interlayer tunnelling connects orbitals of opposite parity in the two layers, leading to a chiral Kondo coupling. We show that the chiral Kondo coupling favors a topological Kondo semimetal at filling $\nu=1+1$, with a non-quantized spin Hall conductance arising from edge modes, whose spectrum and overlap with bulk states we determine. We further show that a spatially random strain field that locally breaks the rotation symmetry can convert the Kondo semimetal to a narrow gap topological Kondo insulator featuring a quantized spin Hall conductance.