Intrinsic and proximity-driven topological superconductivity

Prompted by the increasing need for miniaturization, reliable scaling and multi-functionality for the next generation of devices, the latest years have witnessed a striking research effort in: (i) spintronics, in which the storage, transmission and processing of information takes place not only through charges, as in conventional electronics, but also via their spin degree of freedom; (ii)two dimensional (2D) layered materials beyond-graphene showing exceptional electric and optical properties; (iii) topological insulators, i.e. materials insulating in their volume, but supporting a flow of charges at their surfaces. Moreover, it is becoming increasingly evident, that by interfacing materials systems with different physical and chemical properties, it is possible to induce unprecedented physical mechanisms which open wide perspectives for the realization of the next generation of robust, energy- sparing and environmental-friendly devices. For instance, by combining superconductors with magnetic materials, superconductivity and spintronics can merge giving rise to proximity-driven unconventional superconducting states, which allows spin transport with minimal heating and dissipation. Moreover, the recent experimental confirmation that topological materials may host low- energy quasiparticles identified in a superconductor as Majorana fermions, indicates topological superconductors as relevant systems for protected quantum computation. Plenty of room is still available for the identification of the most suitable material combinations merging relevant functionalities with controllable scalability and miniaturization. In this perspective, the key objective of this proposal is the in-depth investigation of intrinsic and proximity-induced superconductivity in selected combinations of nitride semiconductors and topological crystalline insulators with 2D layered systems, to identify a new platform for unconventional superconductivity and to stabilize Majorana fermions. We will adapt the extensive protocol of crystal growth, advanced (nano)characterization and theoretical analysis developed in the frame of previously granted projects which has allowed us to demonstrate that the controlled correlation and reproducibility of fabrication parameters, structural arrangement and physical/chemical properties of magnetically doped (nitride) semiconductors and insulators leads to striking functionalities. Substantially based on the study of the interplay between interface effects, exchange interaction, spin-orbit coupling and superconducting correlations, the proposed research plan is likely to have remarkable impact on the identification of key material systems and generally on the prospects of topological matter, 2D materials and unconventional superconductivity, expected to play a major role in the forthcoming developments of information processing.

Quantum materials have unusual properties that, once understood and controlled, could enable the next generation of extremely energy-efficient, fast and accurate devices. The extraordinary nature of quantum materials results from interactions that occur at the atomic and subatomic level, where solid matter loses its conventional order and quantum phenomena emerge. In the frame of this project, we have refined the protocol of fabrication and advanced characterization that we had developed earlier and we have extended it to new classes of materials and structures, with the aim of identifying emerging mechanisms originating at the interface of topological insulators, two-dimensional (2D) layered systems and superconductors. In particular, we have contributed to: (i) opening new perspectives for the control of optical/magnetic interactions and of quantum anomalies in two-dimensional material systems; (ii) lying the foundations for developing platforms combining 2D systems and topological insulators; (iii) the understanding of the robust superconductivity coexisting with magnetism in magnetically doped nitrides. Moreover, we have paved the way to the understanding and control of antiferromagnetic 2D layered structures and designed and realized a system which allows performing full-rotation angular dependent magnetotransport measurements at high magnetic fields and cryogenic temperatures. Our results are expected to have a significant impact on the understanding and control next of hybrid heterostructures as building-blocks for the next generation of non-volatile, energy-sparing devices. Moreover, these structures can be developed as active elements for the detection of, for instance, elusive dark matter and ultra-weak magnetic fields.