# Heterogeneous Ta-dichalcogenide bilayer: heavy fermions or doped Mott physics?

## TL;DR

This paper investigates Ta-dichalcogenide heterostructures, revealing that they behave more like doped Mott insulators with charge transfer and hybridization effects, rather than heavy fermion systems, offering new avenues for quantum materials engineering.

## Contribution

First-principles calculations show significant charge transfer and hybridization in Ta-dichalcogenide heterostructures, clarifying their nature as doped Mott insulators rather than heavy fermion systems.

## Key findings

- Charge transfer of 0.4-0.6 electrons from 1T to 1H layers
- System is closer to a doped Mott insulator than heavy fermion behavior
- Quantified interlayer hybridization strength

## Abstract

Controlling and understanding electron correlations in quantum matter is one of the most challenging tasks in materials engineering. In the past years a plethora of new puzzling correlated states have been found by carefully stacking and twisting two-dimensional van der Waals materials of different kind. Unique to these stacked structures is the emergence of correlated phases not foreseeable from the single layers alone. In Ta-dichalcogenide heterostructures made of a good metallic 1H- and a Mott-insulating 1T-layer, recent reports have evidenced a cross-breed itinerant and localized nature of the electronic excitations, similar to what is typically found in heavy fermion systems. Here, we put forward a new interpretation based on first-principles calculations which indicates a sizeable charge transfer of electrons (0.4-0.6 e) from 1T to 1H layers at an elevated interlayer distance. We accurately quantify the strength of the interlayer hybridization which allows us to unambiguously determine that the system is much closer to a doped Mott insulator than to a heavy fermion scenario. Ta-based heterolayers provide therefore a new ground for quantum-materials engineering in the regime of heavily doped Mott insulators hybridized with metallic states at a van der Waals distance.