Aurélien MANCHON
Orbitronics, based on the generation and manipulation of orbital angular momentum, offers interesting perspectives for the conception of alternative microelectronic components. Nonetheless, before any workable device can be realized, efficient means to generate, propagate and detect orbital information must be identified. In this presentation, I will discuss two methods to generate orbital angular momentum out of equilibrium: the orbital Rashba effect and the orbital Hall effect. The former generates nonequilibrium orbital densities whereas the latter unlocks flows of charge-neutral orbital momentum. I will discuss these two mechanisms in different classes of materials, using toy model [1,3] and realistic calculations [2]. In particular, I will demonstrate that the nonequilibrium orbital momentum not only arises from intra-atomic contribution, but also possess an inter-atomic contribution that can be substantial. I will then discuss numerical simulations of both contributions in selected materials of highest interest for experimental realization, using Wannier interpolation of realistic band structures obtained from ab initio calculations. I will show that inter-atomic contribution tends to dominate over the intra-atomic one in the vicinity of the gap of narrow-gap semiconductors (SnTe, PbTe), whereas intra-atomic contribution dominates in large-gap semiconductors (MoS2) as well as in transition metals (V and Pt). These results open appealing perspectives for the realization of efficient sources of orbital angular momentum currents for electrically controlled orbitronics devices.
[1] Manchon et al. Physical Review B 101, 174423 (2020)[2] Pezo et al., arXiv:2201.05807 (2021)
[3] Caruana et al., unpublished