Tom DVIR “Probing the spin and charge ofsuperconducting proximitized nanowires using quantum dots”

Tom Dvir, University Delft

The possibility of topological superconductivity attracts much attention in the recent decade. This interest is due both for fundamental reasons and for the promise it holds for quantum computation. There are many proposals of how to realize such a state. One of them relies on combining three components : a semiconducting nanowire containing spin-orbit coupling, a trivial superconductor, and an in-plane magnetic field. This experimental system was realized in many experiments, whose goal was the observe the zero-bias Majorana edge modes predicted to accompany the topological phase. However, such zero-bias peaks can arise from various mechanisms and cannot, by themselves, serve as the only signature for the topological phase. Thus, the system’s bulk properties, especially the bulk gap, are a complementary object of study searching for topological superconductivity.

I will introduce non-local measurements as a tool that probes the bulk gap in nanowires. Thus, we can distinguish between the signal that arises from local disorder to the system’s global phase. Next, I will show that by replacing tunnel junctions with a quantum dot, we learn about the system’s properties beyond the density of states. We detect the chargeless nature of the proximitized system’s excitations and observe spin polarization in the band structure. These tools will serve to distinguish between the trivial and topological superconducting phases.