Scanning Probe Study of Topological Insulator Josephson Junctions

We present progress towards testing for Majorana bound states in superconductor-topological insulator (S-TI) heterostructures. In a seminal paper in 2008, Fu and Kane predicted the existence of Majorana bound states in planar S-TI-S Josephson junctions with a phase difference of π. There has since been intensive experimental work to realize this system and look for signatures of Majorana bound states. Our approach is to spectroscopically probe superconducting Nb islands deposited on the topological insulator Bi₂Se₃, employing both bulk crystals and thin-film materials. The goal is to detect Majorana signatures in Josephson vortices on the surface with scanning probe methods. Scanning tunneling microscopy measurements and numerical simulations will be presented.