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

Abstract

Recently, the existence of local magnetic moment in a hydrogen adatom on graphene has been confirmed experimentally [González-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.

Distinguishing Majorana zero modes from impurity states through time-resolved transport

“…The steady-state dI/dV signals of cases (2)-(5) look qualitatively similar showing a zero-bias peak (figure 3(a)) as we tuned the magnetic impurity with the parameter forṼ Z to appear close to zero energy, like the MZM. The resonances corresponding to the magnetic impurities around zero energy are broadened compared to the MZM for <  J J due to an increased effective tunnel barrier [77][78][79][80][81]. The broadening of the MZM resonance is therefore systematically narrower than the one of IS.…”

Hydrogen-induced magnetism in graphene: a simple effective model description

“…The magnetic phase diagram of the adatom on graphene has been intensively studied [13,[27][28][29][30]. With proper parameters, the adatom will become magnetic with n ↑ = n ↓ .…”

Local magnetic moment oscillation around an Anderson impurity on graphene

“…Anderson impurity on graphene has been intensively studied in last decade, and its magnetic phase diagram is well known [26,27]. Here, we use the mean field approximation and do not consider the Kondo physics [42][43][44][45][46].…”

“…We use the T -matrix approach [17,19,20,24,39] to calculate this impurity model. Since it is a TB Hamiltonian in Eq.…”

“…Graphene with adsorbed atoms can be well described by the Anderson impurity model [25]. Distinct from other kinds of defects, e.g., vacancy, substitutional impurity, an Anderson impurity is not a simple local potential * jinhua@hust.edu.cn perturbation, but can be magnetic or nonmagnetic depending on its parameters [26,27]. It implies that the FO resulted from an Anderson impurity should be more complex than that induced by a potential impurity, since that the spin degree of freedom has to be considered.…”