Jens Wiebe, Privatdocent at the University of Hamburg is the next invited speaker of the Wigner Colloquia. The title of his lecture is: Atom-by-atom engineering of magnet-superconductor hybrid systems towards the realization of Majorana quasiparticles.
Abstract of his lecture:
Magnetic chains on s-wave superconductors evoke so-called Shiba bands inside the gap of the substrate. If these bands experience sufficiently strong spin-orbit couplings and overlap with the Fermi energy, a topologically nontrivial minigap can open up which may protect zero energy Majorana bound states localized at the chains two ends. We study artificial spin chains, built atom-by-atom [1], with respect to such phenomena. By variation of substrate and adatom species and interatomic distances in the chain [2-5], we adjust the energies of the multi-orbital Yu-Shiba-Rusinov states induced by the adatoms [2,3], their hybridizations [4], as well as the chains’ spin structures [5].
This enables us to tailor the multi-orbital Shiba bands formed by hybridizing Yu-Shiba-Rusinov states such that topologically nontrivial minigaps open [6] and precursors of Majorana bound states appear [7]. Due to a narrow energetical width of the topological minigaps in the systems realized to date, the two components of the Majorana precursors from the two chain ends strongly hybridize, such that a desired protection by the topological minigap is not yet achieved. Here, I will review our work, present our most recent strategies in order to increase the width of the topological minigap [8-11], and show experimental methods we developed to decide on the topologically trivial or non-trivial nature of close-to-zero-energy end states [12]. I will also present very recent results in coupling spins
on superconducting surfaces to quantum dots [13].
I acknowledge funding by the German Research Foundation (DFG) via the Cluster of Excellence ’Advanced Imaging of Matter’ (EXC 2056-project ID 390715994).
The lecture can also be followed on Zoom
Meeting ID: 826 5155 5597
Security Passcode: 37914
Invite Link: https://wigner-hu.zoom.us/j/82651555597?pwd=tw77sJemGDgyahLUyz9uqaVEHUDJh8.1
The lecturer's short biography
Jens Wiebe studied physics and mathematics at the RWTH Aachen University, continued to study physics at the Heidelberg University and received his diploma degree in 1997 for research on second-sound in superfluid 4He. He did his PhD (1998 – 2003) in the research group of Prof. Dr. R. Wiesendanger, Universität Hamburg, on spin-resolved scanning tunnel spectroscopy of disordered two-dimensional semiconductor electron systems. Since 2003, he is a permanent staff member of this research group. In 2020 he finished his Habilitation (Privatdozent) at Universität Hamburg on artificial atomic-spin arrays on solid surfaces.
References
1. D.-J. Choi, N. Lorente, J. Wiebe, K. von Bergmann, A. F. Otte, and A. J. Heinrich,
Rev. Mod. Phys. 91, 041001 (2019).
2. L. Schneider, M. Steinbrecher L. Rózsa, J. Bouaziz, K. Palotás, M. dos Santos Dias, S. Lounis,
J. Wiebe, and R. Wiesendanger, npj Quantum Materials 4, 42 (2019).
3. L. Schneider, S. Brinker, M. Steinbrecher, J. Hermenau, Th. Posske, M. dos Santos Dias,
S. Lounis, R. Wiesendanger, and J. Wiebe, Nature Commun. 11, 4707 (2020).
4. P. Beck, L. Schneider, L. Rózsa, K. Palotás, A. Lászlóffy, L. Szunyogh,
J. Wiebe, and R. Wiesendanger, Nature Commun. 12, 2040 (2021).
5. L. Schneider, P. Beck, J. Wiebe, and R. Wiesendanger, Science Advances 7, eabd7302 (2021).
6. L. Schneider, P. Beck, T. Posske, D. Crawford, E. Mascot, S. Rachel, R. Wiesendanger, and J. Wiebe,
Nature Physics 17, 943 (2021).
7. L. Schneider, P. Beck, J. Neuhaus-Steinmetz, T. Posske, J. Wiebe, and R. Wiesendanger,
Nature Nanotechnology 17, 384 (2022).
8. P. Beck, L. Schneider, L. Bachmann, J. Wiebe, and R. Wiesendanger,
Phys. Rev. Materials 6, 024801 (2022).
9. Ph. Beck, B. Nyári, L. Schneider, L. Rózsa, A. Lászlóffy, K. Palotás, L. Szunyogh, B. Ujfalussy,
J. Wiebe, and R. Wiesendanger, Communications Physics 6, 83 (2023).
10. P. Beck, L. Schneider, R. Wiesendanger, and J. Wiebe, arXiv:2205.10062 [cond-mat.supr-con] (2022).
11. P. Beck, L. Schneider, R. Wiesendanger, and J. Wiebe, Phys. Rev. B 107, 024426 (2023).
12. L. Schneider, Ph. Beck, L. Rozsa, Th. Posske, J. Wiebe, and R. Wiesendanger,
Nature Commun. 14, 2742 (2023).
13. L. Schneider, K. That Ton, I. Ioannidis, J. Neuhaus-Steinmetz, T. Posske, R. Wiesendanger, and J. Wiebe,
Nature 621, 60 (2023).
