Spin-orbitronics in the nanoworld
Samir Lounis
Martin-Luther University Halle-Wittenberg, Halle (Saale) Germany
The interplay of spin, charge, and orbital degrees of freedom—further enriched by topological and chiral effects—gives rise to quantum phenomena spanning broad length and time scales. These effects are at the heart of the rapidly evolving field of spin-orbitronics and play a pivotal role in advancing quantum information technologies. The overarching goal is to enable faster, smaller, and more energy-efficient data storage by developing novel methods to define, control, and detect information bits. In this colloquium, I will discuss magnetic-state manipulation and magneto-transport phenomena across multiple length scales. I will begin with an overview of spin-excitation detection in atomically engineered nanostructures, focusing on insights gained from scanning tunneling spectroscopy. In particular, I will present evidence that the widely observed zero-bias transport anomalies – long attributed to Kondo resonances – are instead manifestations of a new many-body state, the spinaron, a quasiparticle emerging from the coupling between electrons and spin excitations [1,2,3]. Shifting from the atomic scale to larger structures, I will then address topological magnetic textures such as skyrmions, which comprise hundreds or thousands of atoms. I will introduce a novel class of magnetoresistance effects that enable electrical detection of these entities [4]. These effects, operable in current-perpendicular-to-plane geometries, are sensitive to the chiral characteristics of topological spin structures—providing a powerful readout mechanism for the growing zoo of predicted and observed magnetic topological states.
[1] J. Bouaziz et al., Nat. Commun. 11, 6112 (2020)
[2] F. Friedrich et al., Nat. Phys. 20, 28 (2024)
[3] N. Noei et al., Nanoletters 23, 8988 (2023)
[4] I. L. Fernandes, S. Blügel, S. Lounis, Nat. Commun. 13, 1576 (2022)