Misfit layer compounds: a platform for heavily-doped two-dimensional transition metal dichalcogenides

TL;DR

This study demonstrates that misfit layer compounds can serve as a platform for heavily doping two-dimensional transition metal dichalcogenides, enabling exploration of their properties at doping levels much higher than traditional methods.

Contribution

We show that misfit compounds formed by stacking NbSe₂ and LaSe layers act as heavily doped 2D TMDs, surpassing doping limits of conventional techniques, opening new avenues for research.

Findings

Misfit compounds achieve doping levels of 0.55-0.6 electrons per Nb atom.

The charge density wave transitions from 3×3 to 2×2 order due to heavy doping.

Misfit compounds can be engineered to explore a wide doping range in 2D TMDs.

Abstract

Transition metal dichalcogenides (TMDs) display a rich variety of instabilities such as spin and charge orders, Ising superconductivity and topological properties. Their physical properties can be controlled by doping in electric double-layer field-effect transistors (FET). However, for the case of single layer NbSe$_2$, FET doping is limited to $\approx 1\times 10^{14}$ cm$^{-2}$, while a somewhat larger charge injection can be obtained via deposition of K atoms. Here, by performing ARPES, STM, quasiparticle interference measurements, and first principles calculations we show that a misfit compound formed by sandwiching NbSe$_2$ and LaSe layers behaves as a NbSe$_2$ single layer with a rigid doping of $0.55-0.6$ electrons per Nb atom or $\approx 6\times 10^{14}$ cm$^{-2}$. Due to this huge doping, the $3\times3$ charge density wave is replaced by a $2\times2$ order with very short coherence length. As a tremendous number of different misfit compounds can be obtained by sandwiching TMDs layers with rock salt or other layers, our work paves the way to the exploration of heavily doped 2D TMDs over an unprecedented wide range of doping.