Masterwork on Engineered Topological Superconductivity in van der Waals Heterostructures

The project entitled Engineered Topological Superconductivity in van der Waals Heterostructures was recently granted by the ERC to Prof. Christian Schönenberger as an Advanced Research Grant, see University News: ERC-Advanced. In the meantime, a team of researchers, PhD students, postdocs and experienced scientists, could be assembled. The journey into a new territory, where groundbreaking findings are to be expected, has thus started. If you are a student who shares our excitement and looking for a Master’s project, join us!

Topological matter is a new research focus with great perspectives. Of particular interest are topological insulators and superconductors where surface states appear within the gap yielding quasiparticles with new properties that are protected by symmetries. While the surface state in a topological insulator is composed of chiral fermions carrying charge and spin, in topological superconductors (SCs) it is pinned to zero energy due to particle‐hole symmetry and composed of fermions that carry neither charge nor spin. Instead, they are non‐abelian fermions: Majorana- and parafermions (MF/PF) that have been proposed for topological quantum computing. Evidence for MFs have been found in nanowires. The scaling‐up challenge, however, requires a platform in which networks of MFs can be realized. In this project we will use graphene-based van der Waals heterostructure for this purpose. The ability of combining high‐mobility graphene with other layered materials, such as transition‐metal dichalcogenide, few‐layer ferromagnets and SCs offers an unprecedented versatility in the design of topological systems by combining Zeeman energy, spin‐orbit and superconducting pairing interaction. We will design 2D quantum matter using different approaches (figure) and couple it to SCs to induce topological superconductivity. The 2D multilayer stacks will be measured by electrical transport experiments at low temperatures. Specifically, the current-phase relation of topological Josephson junctions and non-local properties of Majorana bound states are of interest.

(a) A set of fabricated encapsulated devices that contain a bilayer of graphene and TMDC. Right: different means to engineer a topological state in graphene. (b) two layer stacked graphene, (c) by proximity to a 2D material with exchange and spin-orbit field, (d) by electric-field (bilayer) and strain tuning and (e) by dressing the band structure with a periodic field, e.g. optical radiation, giving rise to so-called Floquet bands that can be non-trivial.

We are looking for a highly motivated student, preferably from the University of Basel, who is keen to explore fundamental aspects of quantum devices. You will design and fabricate your own devices made from 2D van der Waals heterostructures using state-of-the-art micro- and nanofabrication technologies including a glove-box stacking system. Electric measurements will be done down to mK temperatures and include DC to RF techniques based on modern cryogenic circuitry, e.g. rf-resonators. We expect that you have a profound understanding of quantum and solid-state physics as it is taught in a physics curriculum. The specific focus of your particular Master’s project will be defined upon request.

To apply, please email to me (Christian.Schoenenberger@unibas.ch) with a short motivation statement.

Christian Schönenberger heads the quantum- & nanoelectronics group, see www.nanoelectronics.ch