Speaker
Description
Topological states, potentially leading to the formation of Majorana fermions, have been predicted to emerge in heterostructures of an s-wave superconductor (SU) and a semiconductor (SE) with substantial spin orbit coupling and a split band structure [1,2]. Incorporation of ferromagnetic materials, such as ferromagnetic insulators (FMI), into the heterostructures constitutes a promising route for providing the Zeeman energy necessary for splitting the SE bands [3]. The initial step towards development of an intrinsically topological trilayer structure is to ensure the adequate strength of magnetic proximity effects at the different combinations of FMI/SE and FMI/SU interfaces [4].
We present a comprehensive study of the magnetic properties in InAs/Pb/EuS/Pb and InAs/EuS/Pb heterostructures, with thicknesses varying from 20 to 40 nm for Pb and 1.5 to 4 nm for EuS. The films have been grown by molecular beam epitaxy (MBE) and e-beam deposition. Polarized neutron reflectometry (PNR) has been used to quantify the extent of the magnetic proximity at the FMI/SU and FMI/SE interfaces, which is crucial for entering the topological phase.
For InAs/Pb/EuS/Pb, we observe an extension of magnetism from the EuS layer into the neighbouring layers at both interfaces. The results reveal a magnetic moment arrangement that is parallel at lower interface and antiparallel at top interface with respect to the spins in EuS layer. On the other hand, for InAs/EuS/Pb, we observe a parallel arrangement of magnetic moments at both InAs/EuS and EuS/Pb interfaces. This magnetic behavior can be attributed to the quality of the EuS/Pb interface, a decisive factor for influencing the arrangement of spins [5]. XMCD measurements contribute information about the elemental magnetism. The results are complemented with X-ray reflectometry, TEM, XRD and SQUID measurements on structure and magnetism. The understanding of the interfacial magnetism will play a pivotal role in the development of the final device structure.
References:
1. Lutchyn, R. M., e.t. al, PRL, 105, 077001 (2010)
2. Sarma, S. D., Nat. Phy., 19, 165 (2023)
3. Escribano, S. D., et. al., NPJ Quantum Mater., 7, 81 (2022)
4. Liu, Y., et. al., Nano Lett., 20, 456 (2020)
5. Bergeret, F. S., et. al., PRB, 69, 174504 (2004)
| Please select the related topic from the list below | Magnetic thin films and interfaces |
|---|
