Abstract

Orbitronics is an emerging field in condensed matter physics that explores the fundamental properties of nonequilibrium orbital angular momentum and its transport, with the aim of using the orbital information of electrons for device applications [1]. While manipulating and transporting orbitally polarized electrons was once thought unfeasible due to orbital quenching in crystals [2], we have recently made key predictions that in non-equilibirum, the orbital information manifests as an active degree of freedom, which can be dynamically generated, transported, and coupled to magnetic orders [3-5]. These predictions have led to discoveries of novel phenomena such as the orbital Hall effect [6], orbital-spin conversion [7], orbital magnetoresistance [8], orbital torque [9], orbital pumping [10], terahertz emission via ultrafast orbital transport [11], and dynamic orbital responses [12].
In this talk, I will present the fundamental physical principles and key mechanisms underpinning the field of orbitronics, namely the dynamical generation of orbital angular momentum, intrinsic orbital Hall transport, and its interplay with magnetism. I will also discuss the opportunities and challenges in this field, outlining promising directions for future research.

References
[1] D. Go et al., Europhys. Lett. 135, 13700 (2021).
[2] C. Kittel, Introduction to Solid State Physics, 8th Edition, Wiley (2004).
[3] D. Go et al., Phys. Rev. Lett. 121, 086602 (2018).
[4] D. Go et al., Phys. Rev. Res. 2, 013177 (2020).
[5] D. Go et al., Phys. Rev. Lett. 130, 246701 (2023).
[6] Y.-G. Choi, D. Go et al., Nature 619, 52 (2023).
[7] S. Ding, D. Go et al., Phys. Rev. Lett. 125, 177201 (2020).
[8] S. Ding, D. Go et al., Phys. Rev. Lett. 128, 067201 (2022).
[9] D. Lee, D. Go et al., Nat. Commun. 12, 6710 (2021).
[10] H. Hyashi, D. Go et al., Nat. Electron. 7, 646 (2024).
[11] T. Seifert, D. Go et al., Nat. Nanotechnol. 18, 1132 (2023).
[12] T. Gao, D. Go et al., Nat. Phys. Online (2024).