Soutenance de thèse de Nianjheng WU ISMO, 9 décembre 2022, Orsay.

Soutenance de thèse de Nianjheng WU Vendredi 9 décembre, 14h00 ISMO

Electronic and Magnetic properties of Molecular layers on 2D materials

ISMO Bâtiment 520 – 598 Rue André Rivière – Orsay Le Guichet Orsay 91400 Essonne Île-de-France

Soutenance de thèse de Nianjheng WU

Electronic and Magnetic properties of Molecular layers on 2D materials

Graphene is single-atom-thick layer of carbon atoms arranged in a honeycomb lattice, which has unique electronic properties caused by a linear energy dispersion. However, graphene displays neither intrinsic magnetism nor spin orbit interaction (SOI). My PhD work describes the attempts to induce SOI and magnetism by coupling graphene with transition metal dichalcogenides (TMDs) or specific metal-organic molecules.
I will present two examples of our methodology. In the first example, I found that the supercurrent induced by superconducting contacts persists even in high out-of-plane magnetic fields in samples coupled to TMDs. We attribute this robustness to quasi-ballistic edge states stabilized by the strong SOIs induced in graphene by WS2.
In the second example, I will present the low temperature magnetoresistance of TbPc2 molecules grafted on graphene, which features universal conductance fluctuations (UCF) of a phase-coherent sample. Interestingly, these UCF display a magnetic field-dependent noise, which is highest at low temperature and low field. A noise spectrum with a 1/f dependence suggests a magnetic two-level system with a wide distribution of field-dependent relaxation times. This indicates anisotropic Ising-like fluctuating magnetic moments on graphene whose characteristic energy barrier decreases with the out-of-plane magnetic field.

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