Thema der Dissertation:
Modulation of electronic and magnetic properties of nanostructures on a monolayer of MoS2/Au(111)
Modulation of electronic and magnetic properties of nanostructures on a monolayer of MoS2/Au(111)
Abstract: Fundamental electronic and magnetic properties of single atoms and molecules depend crucially on their immediate environment. Understanding its exact influence allows for the manipulation and thus tailoring of said properties. In this thesis, we investigate different nanostructures on a monolayer of MoS2/Au(111) by means of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM).
We investigated the magnetic properties of single iron atoms on the MoS2 monolayer. We found that the exact position of the atoms in the moiré superstructure, which forms due to the lattice missmatch of the MoS2 and the underlying Au(111), has a crucial impact on those properties. Atoms on the moiré minimum exhibit an inelastic excitation, which is a signature of a spin-flip excitation and atoms on the moiré maximum show a Kondo resonance, which is a sign of increased spin screening by the substrate electrons. The transition between those two observed features was continuous along the moiré structure. We explain these changes by a local variation of the density of states along the moiré modulation.
An impact of the moiré was also observed on single manganese atoms: they exhibit a Kondo resonance in the weak coupling regime, with the amplitude varying along the moiré. We were able to manipulate single manganese atoms into dimers and found three distinct regimes of interatomic exchange coupling, depending on their atom separation. We focused on the dimers with the closest spacing of one atomic lattice site. They show a direct exchange, coupling, which leads to a singlet ground state. The excitation energy from the ground state to the excited triplet state also varies along the moiré structure. In a model calculation we establish that the hybridisation of manganese d-levels with substrate electrons leads to a renormalisation of the singlet-triplet excitation energy. A comparison of experimental values and theoretical prediction suggests that several conduction channels are involved in the renormalisation.
We investigated the magnetic properties of single iron atoms on the MoS2 monolayer. We found that the exact position of the atoms in the moiré superstructure, which forms due to the lattice missmatch of the MoS2 and the underlying Au(111), has a crucial impact on those properties. Atoms on the moiré minimum exhibit an inelastic excitation, which is a signature of a spin-flip excitation and atoms on the moiré maximum show a Kondo resonance, which is a sign of increased spin screening by the substrate electrons. The transition between those two observed features was continuous along the moiré structure. We explain these changes by a local variation of the density of states along the moiré modulation.
An impact of the moiré was also observed on single manganese atoms: they exhibit a Kondo resonance in the weak coupling regime, with the amplitude varying along the moiré. We were able to manipulate single manganese atoms into dimers and found three distinct regimes of interatomic exchange coupling, depending on their atom separation. We focused on the dimers with the closest spacing of one atomic lattice site. They show a direct exchange, coupling, which leads to a singlet ground state. The excitation energy from the ground state to the excited triplet state also varies along the moiré structure. In a model calculation we establish that the hybridisation of manganese d-levels with substrate electrons leads to a renormalisation of the singlet-triplet excitation energy. A comparison of experimental values and theoretical prediction suggests that several conduction channels are involved in the renormalisation.
Zeit & Ort
11.08.2023 | 14:30
Hörsaal A (1.3.14) - Fachbereich Physik, Arnimallee 14, 14195 Berlin