Non-coplanar magnet superconductor hybrid systems

• Applicant: Privatdozentin Dr. Kirsten von Bergmann
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552644472

Magnet superconductor hybrid (MSH) systems are promising candidates for novel emerging phenomena and intense experimental efforts have been undertaken to study zero or one-dimensional magnetic structures on the surfaces of superconductors. In contrast, experimental studies of MSH systems consisting of two-dimensional magnetic films are sparce, even though numerous theoretical investigations have been reported. In particular non-coplanar magnetic order in two-dimensional MSH systems has been proposed to induce topological superconductivity, Majorana bound states, or chiral edge states. Non-coplanar magnetic order in thin films can arise due to the competition of different interactions, in particular frustrated exchange, Dzyaloshinskii-Moriya, or higher-order interactions. One of the most prominent non-coplanar magnetic states, the skyrmion, is often induced by applied magnetic fields which, however, are detrimental to superconductivity. We have identified different experimental approaches to prepare model-type non-coplanar MSH systems. Different constraints need to be taken into account such as the origin of the non-coplanar spin texture in relation to the symmetry of the sample, and its stability below the critical magnetic field of the superconductor. We will use spin-polarized scanning tunneling microscopy at low temperatures to characterize the magnetic order of MSH systems. This experimental method is particularly suited to study atomic-scale magnetic states because it combines spin sensitivity with atomic resolution. At the same time tunnel spectroscopy will be used to investigate the superconducting properties, in particular the in-gap states arising from the interplay of the local magnetic order and the superconducting phase. Moreover, the tip can be used to locally modify the magnetic state with vertical currents or electric fields, enabling a disentanglement of structural, electronic, and magnetic effects. The preparation of non-coplanar model-type MSH systems and their systematic study regarding the interplay of spin texture and superconductivity will facilitate a fundamental understanding of the emerging phenomena.

• DFG Programme: Research Grants