Apparent Kondo effect in Moir\'e TMD bilayers: Heavy fermions or disorder?

TL;DR

This paper questions whether the observed Kondo-like features in Moiré TMD bilayers are due to a true Kondo lattice or can be explained by impurity and phonon scattering, urging further investigation.

Contribution

It provides an alternative explanation for the experimental resistivity data, challenging the interpretation of a Kondo lattice in the original study.

Findings

Impurity and phonon scattering can mimic Kondo signatures in resistivity data.

The observed heavy fermion behavior may not require a Kondo lattice formation.

Further experimental verification is necessary to confirm the Kondo effect in this system.

Abstract

A recent work by Zhao et al. [1] reports the realization of a synthetic Kondo lattice in a gate-tunable Moir\'e TMD bilayer system. The observation of a Kondo lattice is supported by a plateau (or dip, depending on filling) in the temperature dependence of the resistivity $\rho(T)$ around $T^*\sim 40~$K, which is interpreted as the Kondo temperature scale, and an apparent enhancement of carrier mass extracted from the low-temperature resistivity data, indicating the emergence of `heavy fermions'. The latter observation is crucially based on the assumption that the primary resistive scattering mechanism is Umklapp electron-electron scattering in the underlying Fermi liquid. In this work, we analyze the experimental data under the assumption that the primary resistive scattering mechanism is not electron-electron scattering, but Coulomb scattering by random quenched charged impurities and phonon scattering. We show that a combination of impurity and phonon scattering is a plausible alternative explanation for the observed resistivity that can describe the key features of the experimental data, even if no Kondo lattice has formed, indicating that further theoretical and experimental work is needed to conclusively verify the formation of a Kondo lattice in Ref. [1]. [1] W. Zhao, B. Shen, Z. Tao, Z. Han, K. Kang, K. Watanabe, T. Taniguchi, K. F. Mak, and J. Shan, arXiv:2211.00263 (2022).