[GS_C_MS] Shaping Orbital Properties of Materials by Chirality, Topology, and Geometry
ABSTRACT
Orbitronics aims to exploit the orbital degree of freedom of electrons as an information carrier in quantum transport, which is an emerging research field established recently [1]. In recent years, orbitally polarized currents have been theoretically predicted [2] and experimentally measured [3], and they can be applied to control and detect magnetic orders in spintronic devices, such as magnetoresistive random access memory (MRAM) [4]. Despite the remarkable progress, however, orbitronics faces fundamental challenges that the field must overcome: (1) unambiguously generating and detecting orbital-polarized currents, (2) ensuring their robustness regardless of imperfections and detailed properties of materials, and (3) sufficiently enhancing their magnitudes.
To overcome these challenges, I propose a material-design approach based on chirality, topology, and geometry. I will explain how chiral symmetry breaking in crystals leads to orbital-momentum locking, which can be harnessed for (1) [5]. Regarding (2), I show how certain classes of chiral crystals can host dispersions of topological semimetals, which we denote as orbital chiral fermions [6]. Finally, I will show how (3) the quantum geometry of wave functions is crucial for orbital magnetism induced by the itinerant circulation of electrons [7]. At the end of the talk, I will share my own ‘big picture’ of where the field is going and an outlook on future directions.
[1] DG et al. Europhys. Lett. 135, 37001 (2021).
[2] DG et al. Phys. Rev. Lett. 121, 086602 (2018).
[3] Y.-G. Choi, D. Go et al. Nature 619, 52 (2023).
[4] D. Jo, DG et al. npj Spintronics 2, 19 (2024).
[5] DG et al. In preparation.
[6] Hagiwara, DG et al. Adv. Mater. 2418040 (2025).
[7] H. Lee, DG et al. arXiv:2603.19875.
