Exploring Topological Interfacial Superconductivity in Quantum Anomalous Hall/Iron Chalcogenide Heterostructures

When two different materials are brought together, the resultant interface between them often shows unexpected quantum phenomena. For example, the interfaces between a material with strong spin-orbit coupling and a superconductor can host an unusual form of superconductivity known as topological superconductivity. Over the past decade, the possibility of realizing topological superconductivity has generated much excitement in the field, mainly due to the potential use of its excitations (i.e. Majoranas) in fault-tolerant topological quantum computations. Magnetic topological insulator, a material with very strong spin-orbit coupling whose hallmark is the quantum anomalous Hall effect, provides a natural platform to pursue topological superconductivity and Majorana physics. In this project, we use molecular beam epitaxy (MBE) to synthesize heterostructures formed by two magnetic materials, a ferromagnetic topological insulator layer and an antiferromagnetic iron chalcogenide layer, specifically Cr-doped (Bi,Sb)2Te3/FeTe. By performing in-situ angle-resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy and spectroscopy (STM/S), and ex-situ electrical transport, reflective magnetic circular dichroism (RCMD), and magnetic force microscopy (MFM) measurements, we systematically investigate and understand the coexistence of superconductivity and ferromagnetism and explore topological interfacial superconductivity in these MBE-grown heterostructures. Our successful synthesis of superconducting heterostructures formed with two magnetic materials and the exploration of the topological interfacial superconductivity and Majorana physics therein will provide an alternative approach for the development of topological quantum computations.