Towards probing zero energy bound states with circuit QED in topological insulator junctions

Abstract

Majorana fermions are aimed to be observed in a spin-non-degenerate system where particle-hole symmetry is imposed. Such a landscape was proposed by Fu and Kane to be formed at the interface between a topological insulator and a superconductor. Topological insulators are insulating materials in the bulk, but that present metallic states with spin non-degeneracy at the surface. These metallic states in the vicinity of an ordinary superconductor become superconducting by proximity effect imposing the particle-hole symmetry, hence an scenario were Majorana fermions observation is possible. Taking first steps towards Majorana engineering, the aim of the thesis is to study the energy band structure of a STIS junction. The STIS junction studied was made from bismuth selenide nanowires and aluminium electrode contacts and then embedded in a RF-SQUID loop coupled to a resonator. This configuration allowed to characterize the band structure of the STIS junction probing its susceptibility through microwave reflectometry measurements. The experimental data was then compared to an STIS short ballistic junction model obtaining a relaxation parameter γD = 2 GHz and a microwave transitions rate of γND = 3 GHz for probing frequency 4.20 GHz and γND = 10 GHz at 8.16 GHz.