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TT: Fachverband Tiefe Temperaturen

TT 40: Spin Transport and Orbitronics, Spin-Hall Effects II (joint session MA/TT)

TT 40.2: Vortrag

Mittwoch, 19. März 2025, 17:45–18:00, H19

Orbital Topology of Chiral Crystals for Orbitronics — •Ying-Jiun Chen¹, Kenta Hagiwara^1,2, Dongwook Go³, Xin Liang Tan^1,2, Sergii Grytsiuk¹, Kui-Hon Ou Yang⁴, Guo-Jiun Shu⁵, Jing Chien⁴, Yi-Hsin Shen⁴, Xiang-Lin Huang⁵, Iulia Cojocariu¹, Vitaliy Feyer^1,2, Minn-Tsong Lin^4,6, Stefan Blügel¹, Claus Michael Schneider^1,2, Yuriy Mokrousov^1,3, and Christian Tusche^1,2 — ¹Forschungszentrum Jülich — ²University of Duisburg-Essen — ³Johannes Gutenberg University Mainz — ⁴National Taiwan University, Taiwan — ⁵National Taipei University of Technology, Taiwan — ⁶Academia Sinica, Taiwan

Chirality is ubiquitous in nature and manifests in a wide range of phenomena including chemical reactions, biological processes, and quantum transport of electrons. In quantum materials, the chirality of fermions, given by the relative directions between the electron spin and momentum, is connected to the band topology of electronic states. Here, we show that in structurally chiral materials like CoSi, the orbital angular momentum (OAM) serves as the main driver of a nontrivial band topology in this new class of unconventional topological semimetals, even when spin-orbit coupling is negligible. A nontrivial orbital-momentum locking of multifold chiral fermions in the bulk leads to a pronounced OAM texture of the helicoid Fermi arcs at the surface. Our findings highlight the pivotal role of the orbital degree of freedom for the chirality and topology of electron states, in general, and pave the way towards the application of topological chiral semimetals in orbitronic devices.

Keywords: Orbital angular momentum; Topological materials; Chiral crystals; Orbitronics; Momentum microscopy