# Effect of doping on lattice instabilities of single-layer 1H-TaS2

## TL;DR

This study uses ab initio calculations to show how electron doping suppresses charge-density-wave instabilities in single-layer 1H-TaS2, aligning with experimental observations and highlighting the roles of electron-phonon interactions and strain.

## Contribution

It provides a detailed theoretical analysis of doping effects on lattice instabilities in monolayer 1H-TaS2, connecting electronic doping to suppression of CDW order.

## Key findings

- Doping removes the lattice instability associated with CDW in monolayer 1H-TaS2.
- Doping causes lattice expansion, influencing stability.
- The stability depends on electron-phonon coupling and phonon energy variations.

## Abstract

Recent ARPES measurements of single-layer 1H-TaS2 grown on Au(111) suggest strong electron doping from the substrate. In addition, STM/STS measurements on this system show suppression of the charge-density-wave (CDW) instability that occurs in bulk 2H-TaS2. We present results from ab initio DFT calculations of free-standing single-layer 1H-TaS2 to explore the effects of doping on the CDW. In the harmonic approximation, we find that a lattice instability along the Gamma-M line occurs in the undoped monolayer, consistent with the bulk 3x3 CDW ordering vector. Doping removes the CDW instability, in agreement with the experimental findings. The doping and momentum dependence of both the electron-phonon coupling and of the bare phonon energy (unscreened by metallic electrons) determine the stability of lattice vibrations. Electron doping also causes an expansion of the lattice, so strain is a secondary but also relevant effect.