PhD Defense: Sven Albrecht – University of Copenhagen

PhD Defense: Sven Albrecht

Quasiparticle dynamics and exponential protection in Majorana islands

Recent advances in the growth of epitaxially matched superconductor-semiconductor interfaces have given rise to new experiments that probe topological superconductivity in InAs/Al half-shell nanowires. Of particular interest is the Majorana island geometry, a mesoscopic Coulomb island with proximity-induced superconductivity, which forms the building block of some Majorana fusion rule and braiding proposals. Measurements on Majorana islands typically show a transition between 2e and 1e-periodic Coulomb oscillations with transport through a discrete zero-energy state at finite magnetic fields, a key signature of Majorana modes in this geometry. In this regard, I will discuss measuring Majorana modes in Coulomb blockade, demonstrate their exponential protection with increasing island length, and show effects of quasiparticle poisoning in Majorana islands.