Masters Defense: Gorm Steffensen – University of Copenhagen

Masters Defense: Gorm Steffensen

Yu-Shiba-Rusinov Bound States in Quantum Dots

Modern experiments using Superconductor-Dot systems show clear signatures of sub-gap Yu-Shiba-Rusinov (YSR) bound states which arise from magnetic interaction between dot and superconductor. In this defence I will present a theoretical description of the YSR state based on a classical-spin approximation and show how this state arises in dot systems. I will then show how it can be measured using a metallic probe and the nature of the non-equilibrium sub-gap transport also prevalent in experimental results. To understand larger double-dot systems I will present a Zero-Band-Width (ZBW) approximation yielding results comparable to those obtained by NRG. Lastly, I will show some perspectives on the issue: Theoretical considerations for future experimental setups and coupling to the broader field of sup-gap transport which is presently a rich field of research.