From topological magnetism to topological superconductivity

Speaker: Dr Roberto Lo Conte (Physics Department, University of Hamburg)

Title: From topological magnetism to topological superconductivity

Abstract: The upcoming revolution in information technology driven by quantum computing has triggered the search for new quantum materials. Hybrid quantum systems, where materials with different properties (magnetism, superconductivity, spin-orbit coupling) are joined together, are expected to host emergent quantum properties such as topological [1] and triplet [2] superconductivity, which can be used for the implementation of fault tolerant quantum computing [3] and the design of ultralow dissipation spintronic devices [4]. In particular, it has been proposed that the combination of topological spin textures - such as magnetic skyrmions - and superconducting materials could lead to the stabilization of topological superconducting states [5,6].

In this talk I will first discuss the stabilization of magnetic skyrmions in thin film multilayers without the requirement of any external magnetic field [7]. This is achieved by tailoring the magnetic properties of multilayers where an interlayer exchange coupling is present between two magnetic layers separated by a non-magnetic spacer. Most importantly, I will explain how, by tailoring the strength of the interlayer coupling, we can tune the size of the stabilized skyrmions. Second, I will discuss our recent investigation of a magnet/superconductor hybrid system consisting of a Mn ultrathin film deposited on top of a superconducting Nb substrate. Our results [8] show an antiferromagnetic order in the Mn thin film which coexists with a proximity-induced superconducting state. Preliminary spectroscopic data suggest that the hybrid system hosts in-gap Yu-Shiba-Rusinov bands [9,10], which could potentially establish topologically protected Majorana modes.

References:

[1]       M. Sato and Y. Ando, Reports Prog. Phys. 80, 076501 (2017).

[2]       J. Linder and J. W. A. Robinson, Nat. Phys. 11, 307 (2015).

[3]       C. W. J. Beenakker, Annu. Rev. Condens. Matter Phys. 4, 113 (2013).

[4]       M. Eschrig, Reports Prog. Phys. 78, 104501 (2015).

[5]       E. Mascot, J. Bedow, M. Graham, S. Rachel, and D. K. Morr, Npj Quantum Mater. 6, 6 (2021).

[6]       J. Bedow, E. Mascot, T. Posske, G. S. Uhrig, R. Wiesendanger, S. Rachel, and D. K. Morr, Phys. Rev. B 102, 180504 (2020).

[7]       R. Lo Conte, A. K. Nandy, G. Chen, A. L. Fernandes Cauduro, A. Maity, C. Ophus, Z. Chen, A. T. N’Diaye, K. Liu, A. K. Schmid, and R. Wiesendanger, Nano Lett. 20, 4739 (2020).

[8]       R. Lo Conte, M. Bazarnik, K. Palotás, L. Rózsa, L. Szunyogh, A. Kubetzka, K. von Bergmann, and R. Wiesendanger, ArXiv 2109.03743, (2021).

[9]       B. W. Heinrich, J. I. Pascual, and K. J. Franke, Prog. Surf. Sci. 93, 1 (2018).

[10]     L. Schneider, P. Beck, T. Posske, D. Crawford, E. Mascot, S. Rachel, R. Wiesendanger, and J. Wiebe, Nat. Phys. 17, 943 (2021).