Manipulating superconductivity at the nanoscale through magnetism and proximity effects

Abstract

In this thesis I studied the interaction of atomic and molecular magnetic impurities with superconductors. I deposited single Mn atoms on the surface of beta-Bi2Pd superconductor and manipulate them on the surface. The classical spin approximation green function approach allow me to describes the Yu-Shiba-Rusinov (YSR) states when the atoms are coupled on the surface in different structures. YSR states also arise close to iron porphyrin magnetic molecules with in-plane magnetic anisotropy due to the ligands that surround Fe. Here I switch to a full quantum spin model approach and describe the rich excitation spectrum. This comprehend a novel Cooper pair-excitation, possible when the magnetic impurity is strongly coupled with the superconductor. This study is done in proximitized Gold on vanadium, where I also characterize the proximity effect. I also studied a different proximity system where we couple Pb islands to graphene. The superconductivity is induced in graphene and the island manipulation allows the tuning and study of how proximity effect changes modifying confinement and island size.