Assembling Chiral Materials into Tunnel Junctions

Abstract

Chiral-induced spin selectivity (CISS) has emerged as a powerful route to generate spin-polarized currents without the need for magnetic order, offering a promising platform for future spintronic applications [1,2]. While conventional spintronic devices rely on a pairs of ferromagnetic electrodes, integrating chiral molecular materials into tunnel junctions opens new possibilities for designing highly efficient spin filters and energy-efficient spin–charge conversion architectures. In this talk, I will present our recent progress on junction devices with lateral π-extended helical nanographenes, which exhibit strong optical activity and remarkably high spin polarization at room temperature. By combining these chiral molecular systems with well-established tunnel barrier engineering, we aim to construct solid-state junctions capable of realizing spintronic functionalities through the CISS effect [3]. We observed
a clear magnetoresistance at room temperature in the tunnel junction devices, which exhibit unidirectional transport properties. This work builds not only on the successful synthesis of the lateral chiral molecules [4] but also on our extensive expertise in tunnel junction investigation, established through recent studies on asymmetric tunnel junctions based on van der Waals antiferromagnetic CrSBr (Nature 2024 [5]) or low-resistivity metal chromium (Nano Lett. 2023 [6]). I will also introduce the design strategies for chiral tunnel junctions, the impact of molecular structure on spin-filtering efficiency, and the outlook of chiral materials tunnel junction devices. This approach paves the way toward next-generation molecular spintronic devices that combine functionality with scalable solid-state integration.

References
[1] B. Bloom et al. Chem. Rev. 124(4), 2014
[2] S. Ham et al. Micromachines 15(4), 528, 2024
[3] S. Yang et al., Nat. Rev. Phys. 3, 328, 2021
[4] W. Niu et al. Angew. Chem. Int. Ed. 63, e202319874, 2024
[5] Y. Chen et al. Nature 632, 1045, 2024
[6] C. Fang et al. Nano Lett. 23, 11485, 2023

Dr. Chi Fang is currently a postdoctoral researcher at the Max Planck Institute of Microstructure Physics, Germany. He received his Ph.D. in Condensed Matter Physics from the University of Chinese Academy of Sciences (UCAS) in 2020 and M. S. in Material Engineering from UCAS in 2017. His research focuses on magnetic tunnel junction and spin transport in antiferromagnets. Dr. Fang has published more than 30 peer-reviewed papers, which received over 1,700 citations with an h-index of 20 according to Web of Science (WoS).