Peter Liljeroth
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 to grow islands of ferromagnetic CrBr3 [2] on a superconducting NbSe2 substrate [3]. 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 [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.
[2] W. Chen, Z. Sun, Z. Wang, L. Gu, X. Xu, S. Wu, C. Gao, Direct observation of van der Waals stacking–dependent interlayer magnetism. Science 366, 983 (2019)
[3] 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, arxiv:2009.13465 (2020)
[4] 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 ferromagnet-superconductor van der Waals heterostructure, arXiv:2002.02141 (2020)