Quantum designer materials that realize electronic responses not found in naturally occurring materials have recently attracted intense interest. For example, topological superconductivity [1] - a key ingredient in topological quantum computing – may not exist in any single material. However, using designer van der Waals (vdW) heterostructures, it is possible to realize the desired physics through the engineered interactions between the different components. We use molecular-beam epitaxy (MBE) to grow islands of ferromagnetic CrBr3 on a superconducting NbSe2 substrate [2]. This combines out of plane ferromagnetism with Rashba spin-orbit interactions and s-wave superconductivity and allows us to realize topological superconductivity in a van der Waals heterostructure [3, 4]. We characterize the resulting one-dimensional edge modes using low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS). Achieving topological superconductivity in a vdW heterostructure facilitates its incorporation in future device structures and potentially allows further control through e.g. electrostatic gating.
References
[1] M. Sato, and Y. Ando, Topological superconductors: a review. Rep. Prog. Phys. 80, 076501 (2017).
[2] S. Kezilebieke, M.N. Huda, O.J. Silveira, V. Vaňo, J. Lahtinen, R. Mansell, S. van Dijken, A.S. Foster, P. Liljeroth, Electronic and magnetic characterization of epitaxial CrBr3 monolayers, Adv. Mater. accepted for publication (arxiv:2009.13465).
[3] S. Kezilebieke, M. N. Huda, V. Vaňo, M. Aapro, S. C. Ganguli, O. J. Silveira, S. Głodzik, A. S. Foster, T. Ojanen, P. Liljeroth, Topological superconductivity in a designer van der Waals heterostructure, Nature 588, 424 (2020).
[4] S. Kezilebieke, V. Vaňo, M.N. Huda, M. Aapro, S.C. Ganguli, P. Liljeroth, J.L. Lado, Moiré-enabled topological superconductivity, arxiv:2011.09760.
Peter Liljeroth (born 1975, Finland) received his Ph.D in physical chemistry and electrochemistry at the Helsinki University of Technology in 2002. Subsequently, Liljeroth was a post-doc at Utrecht University (2003-2006) and IBM Zurich Research Laboratory (2006–2007) working on low-temperature scanning probe microscopy. Before his present appointment (2011-) as a professor at the Department of Applied Physics, Aalto University (Finland), he was an assistant professor at Utrecht University (2007–2010).
Prof. Liljeroth has published 94 peer-reviewed articles (h-index of 41). He was awarded the ERC Starting Grant ("Atomically precise nanoelectronic materials") in 2011, ERC Advanced Grant (”Artificial designer materials”) in 2018, and he is currently holds a post of an Academy Professor from the Academy of Finland (2019-2023).
Prof. Liljeroth heads the Atomic Scale Physics group at Aalto University. His group focusses on probing the atomic scale structure and electronic properties of molecules and atomically well-defined nanostructures using low-temperature scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). These techniques make it possible structurally and electronically characterise and manipulate matter one atom at the time. The most recent topics include designer quantum states in van der Waals heterostructures, metal-organic frameworks and engineered atomic lattices, and molecular structure determination at the single molecule level by AFM.