PGI-1 Talk: Oliver Busch

Quantum Theory of Materials Seminar

Steady-state and ultrafast transport of orbital angular momentum

S electrons can generate orbital currents via the orbital Hall effect (OHE) [1]. This might appear unexpected because s electrons in a single atom cannot carry orbital angular momentum (OAM). However, since electrons propagate over numerous atoms in a solid, they can move on trajectories that transport OAM, nonetheless. We observe such cycloid trajectories for the geometrical edge states of a Kagome lattice where OAM is generated by inter-site contributions [2]. This alternative mechanism reveals that the steady-state OHE is a much more prevalent phenomenon than was expected before, rendering it even more significant for dissipation-less orbitronic applications.

In electron dynamics simulations with our computational framework EVOLVE [3], we are able to compute OAM and OAM currents with femtosecond and atomic resolution in a nanoribbon [4]. We observe both accumulation of OAM and transverse OAM currents, i.e. an OHE, induced by a femtosecond laser pulse. Thus, we are able to extend the steady OHE to the ultrafast time domain. As we demonstrate, the transverse OAM current is not proportional to the laser's electric field, like in the steady OHE, but they are shifted in time akin to the velocity and driving force of a classical driven harmonic oscillator.

[1] O. Busch et al., Physical Review Research 5, 043052 (2023)
[2] A. Pezo et al., Physical Review B 106, 104414 (2022)
[3] F. Töpler et al., New Journal of Physics 23, 033042 (2021)
[4] O. Busch et al., arXiv:2307.08444 (2023)

Contact

Dr. Dongwook Go
Phone: +49 2461 61-4399
Email: d.go@fz-juelich.de

Oliver Busch
Institute of Physics, Martin-Luther University Halle-Wittenberg
Email: oliver.busch@physik.uni-halle.de