# Fano-shaped impurity spectral density, electric-field-induced in-gap state and local magnetic moment of an adatom on trilayer graphene

## TL;DR

This paper theoretically studies how an adatom on trilayer graphene exhibits unique impurity spectral features, electric-field-tunable in-gap states, and magnetic moments, revealing stacking and electric field effects distinct from monolayer graphene.

## Contribution

It introduces a detailed theoretical analysis of impurity states and magnetic moments of adatoms on trilayer graphene, highlighting electric field control and stacking order effects.

## Key findings

- Fano-shaped impurity spectral density on r-TLG
- Electric field can induce in-gap impurity states
- Impurity magnetic phase depends on electric field direction

## Abstract

Recently, the existence of local magnetic moment in a hydrogen adatom on graphene has been confirmed experimentally [Gonz\'{a}lez-Herrero et al., Science, 2016, 352, 437]. Inspired by this breakthrough, we theoretically investigate the top-site adatom on trilayer graphene (TLG) by solving the Anderson impurity model via self-consistent mean field method. The influence of the stacking order, the adsorption site and external electric field are carefully considered. We find that, due to its unique electronic structure, the situation of the TLG is drastically different from that of the monolayer graphene. Firstly, the adatom on rhombohedral stacked TLG (r-TLG) can have a Fano-shaped impurity spectral density, instead of the normal Lorentzian-like one, when the impurity level is around the Fermi level. Secondly, the impurity level of the adatom on r-TLG can be tuned into an in-gap state by an external electric field, which strongly depends on the direction of the applied electric field and can significantly affect the local magnetic moment formation. Finally, we systematically calculate the impurity magnetic phase diagrams, considering various stacking orders, adsorption sites, doping and electric field. We show that, because of the in-gap state, the impurity magnetic phase of r-TLG will obviously depend on the direction of the applied electric field as well. All our theoretical results can be readily tested in experiment, and may give a comprehensive understanding about the local magnetic moment of adatom on TLG.