General scheme for stable single and multiatom nanomagnets according to symmetry selection rules

Abstract

At low temperature, information can be stored in the orientation of the localized magnetic moment of an adatom. However, scattering of electrons and phonons with the nanomagnet leads its state to have incoherent classical dynamics and might cause fast loss of the encoded information. Recently, it has been understood that such scattering obeys certain selection rules due to the symmetries of the system. By analyzing the point-group symmetry of the surface, the time-reversal symmetry and the magnitude of the adatom effective spin, we identify which nanomagnet configurations are to be avoided and which are promising to encode a stable bit. A new tool of investigation is introduced and exploited: the quasispin quantum number. By means of this tool, our results are easily generalized to a broad class of bipartite cluster configurations where adatoms are coupled through Heisenberg-like interactions. Finally, to make contact with the experiments, numerical simulations have been performed to show how such stable configurations respond to typical scanning tunneling microscopy measurements.

Magnetic properties of single rare-earth atoms on graphene/Ir(111)

“…As described in Refs. [25,26], in C 6v symmetry, the CF Hamiltonian can be expressed in terms of a reduced set of Stevens operatorsÔ …”

Electron-assisted magnetization tunneling in single spin systems

“…In this case, care has to be taken when analyzing magnetic stability. As has already been reported 10,17,18 , two inherent symmetries of H CF play an important role for the properties of the atom wavefunction: the rotational symmetry and the time-inversion symmetry.…”

“…A. M. Marciani et al (2017) The paper by Marciani et al 17 uses an approach very similar to ours. However, we disagree with several points of the analysis.…”

“…Time-inversion symmetry: The Hamiltonian H CF is due to the electrostatic interactions and thus H CF has to commute with the time reversal operator T (see [17][18][19] ). T is antiunitary, i.e.…”

Enhanced lifetimes of spin chains coupled to chiral edge states

“…Relaxation times for 3d atoms on metals range from the ps time scale for magnetic atoms directly on a conducting substrate [19] up to tens of ms [20] in the presence of a decoupling layer. In addition, the role of the symmetry of the adsorption site have been highlighted [21][22][23][24]. This has permitted reaching the single atom limit bit by depositing Ho atoms on a MgO/Ag(100) surface [10,23] with relaxation times exceeding hours observed.…”