Bound States of Charged Adatoms on MoS2: Screening and Multivalley Effects

TL;DR

This paper investigates how charged adatoms create bound states on MoS2, revealing complex valley-dependent behaviors and providing insights relevant for electronic property control in 2D materials.

Contribution

It introduces large-scale tight-binding simulations with ab initio screened potentials to analyze impurity states in MoS2, highlighting multivalley effects and state crossovers.

Findings

Multiple impurity states with valley-dependent characteristics

Impurity state energies and wavefunctions mapped near adatoms

Crossovers of impurity states at critical charge strengths

Abstract

Adsorbate engineering is a promising route for controlling the electronic properties of monolayer transition-metal dichalcogenide materials. Here, we study shallow bound states induced by charged adatoms on MoS$_2$ using large-scale tight-binding simulations with screened adatom potentials obtained from ab initio calculations. The interplay of unconventional screening in two-dimensional systems and multivalley effects in the transition-metal dichalcogenide (TMDC) band structure results in a rich diversity of bound impurity states. We present results for impurity state wavefunctions and energies, as well as for the local density of states in the vicinity of the adatom which can be measured using scanning tunnelling spectroscopy. We find that the presence of several distinct valleys in the MoS$_2$ band structure gives rise to crossovers of impurity states at critical charge strengths, altering the orbital character of the most strongly bound state. We compare our results to simpler methods, such as the 2D hydrogen atom and effective mass theory, and we discuss limitations of these approaches.