Superconducting tunneling spectroscopy of graphene and graphene nanostructures

Tunneling spectroscopy;Graphene;Nanostructures;Andreev bound states;Coulomb Blockade;Molybdenum disulfide

Li, Yanjing

关键词: Tunneling spectroscopy;    Graphene;    Nanostructures;    Andreev bound states;    Coulomb Blockade;    Molybdenum disulfide;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49557/Yanjing_Li.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This dissertation is concerned with superconducting tunneling spectroscopy of graphene and nanostructures in two dimensional materials. The technique of tunneling spectroscopy via a planar superconducting probe is developed based on a well-formed self-limited tunnel barrier created only between the Pb and the graphene. High magnetic field/low temperature spectroscopy is performed on graphene devices, and manifests energy-dependent features such as scattering resonances and localization behavior. This superconducting tunnel technique is also used to study graphene nanostructures, which can host quantum dot(s) and thus support Andreev bound states (ABS). The fact that ABS are observed only in the narrow (10 nm wide) nano constriction stresses the importance of coupling between the quantum dot and the contact leads for the observation of ABS.The reason why the quantum dot in the narrow constriction has a better coupling to contact leads is likely due to fact that the size of the constriction is smaller than the characteristic length of the potential disorder, which exists in the two dimensional material subject to charge impurities on the substrate. We extend the nanostructure study to another two dimensional material, molybdenum disulfide (MoS2), where we observe the evolution of the system from a regime of Coulomb blockade to resonant transmission. Our observation could open up new possible applications using nanostructure in these low dimensional materials.