Magnetic proximity in semiconductor–superconductor–ferromagnetic epitaxial systems
A promising class of topological states knows as Majorana fermions (MFs), has opened the exciting path of fault tolerant quantum computing. It has been predicted that MFs can exist in conventional solid-state systems e.g. one-dimensional semiconductor (SE) nanowire coupled to a superconductor (SU) in presence of a strong Zeeman field. However, the impracticality associated with large magnetic fields (> 1 T) in terms of device layout and its detrimental impact on superconductivity propels integration of ferromagnetic insulators (FMI). A magnetic exchange coupling at an SE or SU interface to a FMI has the potential to replace the need for external magnetic field and realize zero-field topological states. This approach may open a new paradigm in quantum technology, however at the expense of stringent material requirements.
The hybrid SE-FMI-SU crystals growth is in early stage, and consequently, impact of bulk and hybrid interface crystalline quality on proximity coupling and subsequent hybridization of the electronic structure is far from being understood. This project aims to reduce the knowledge gap. We target to, iteratively (i) quantify extent of proximity induced magnetism across interfaces and the impact of bulk and/or interface disorder in SE-FMI-SU hybrid structures, and (ii) optimize SE-SU-FMI growth and explore new material combinations for realizing a scalable quantum technology. The high interface sensitivity of PNR makes it a technique of choice, which we will complement with techniques like SQUID magnetometry, X-ray magnetic circular dichroism and transmission electron microscopy.