Majorana in Chains and Hinges

In recent years, following pioneering theoretical work of Kitaev and others, we have learned how to engineer materials that harbor quasiparticles that behave similar to fermions that Majorana had first envisioned. In particular, there has been a focus on one-dimensional topological superconductor that harbor Majorana zero modes (MZM) that can potentially be used to make fault-tolerant topological quantum computation possible. We have proposed and implemented a platform for realization of topological superconductivity and MZM in chains of magnetic atoms on the surface of a superconductor. In this talk, I will describe the series of experiments on this platform that we have performed to establish the presence of these exotic quasi-particle using spectroscopic mapping with the scanning tunneling microscope (STM). These include the most recent study of the unique spin signature of MZM. I will also describe work on a new platform where we use the one-dimensional helical hinge states of a higher order topological insulators. In paritcular, I will show experiment demonstrating how combination of magentism and superconductivity on such one-dimensional states can also give rise to MZM that can be detected with an STM. Overall these experiments, illustrate how the power of spectroscopic imaging with the STM can be used to characterize novel quantum states of matter and visualize their exotic quasi-particles.