Topological superconductivity in a van der Waals heterostructure

Peter Liljeroth

There has been a surge of interest in designer materials that would realize electronic responses not found in naturally occurring materials. For example, it is not clear if topological superconductivity [1], which is a key ingredient in topological quantum computing, exist in any single material. These limitations can be overcome in designer van der Waals (vdW) heterostructures, where the desired physics emerges from the engineered interactions between the different components.
Molecular-beam epitaxy (MBE) growth allows the construction of vertical heterostructures with clean and high-quality interfaces [2]. We use MBE to grow islands of ferromagnetic CrBr3 [3] on a superconducting NbSe2 substrate. This combines out of plane ferromagnetism with Rashba spin-orbit interactions and s-wave superconductivity and allows us to realizate 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). The use of vdW heterostructures with uniform and high-quality interfaces is promising for future device structures and further control of topological superconductivity through external stimuli (e.g. electrostatic gating).

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[2] S. Kezilebieke, M. N. Huda, P. Dreher, I. Manninen, Y. Zhou, J. Sainio, R. Mansell, M.M. Ugeda, S. van Dijken, H.-P. Komsa, P. Liljeroth, Electronic and Magnetic Characterization of Epitaxial VSe2 Monolayers on Superconducting NbSe2, Commun. Phys. 3, 116 (2020)
[3] 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)
[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)