Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 26: Ultra-fast phenomena

HL 26.2: Talk

Wednesday, March 14, 2018, 09:45–10:00, EW 202

Ultra-fast buildup of toroidal moments in nanostructures driven by topological light fields — •Jonas Wätzel and Jamal Berakdar — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Karl-Freiherr-Von-Fritsch-Str. 3, 06112 Halle (Saale)

The interaction of structured light fields with matter opens the door to exciting effects and mechanisms beyond the optical dipole selection rules. For instance, we demonstrated in the past that optical vortices transfer angular momentum to the charge density which can be used to manipulate and steer the carrier dynamics. A direct consequence is the possibility to generate a sizable, directed photocurrent.

Here we report on the irradiation of a three-dimensional semiconductor ring by radially polarized vector beams. An appropriate combination with conventional linear polarized light pulses renders possible the generation of solenoid current loops in the torus. As a consequence a circulating magnetic moment is produced which is accompanied by a toroidal moment in the center which is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles.

The direction and magnitude of this toroidal moment can be steered and controlled at will on an ultra-fast time scale by changing the pulse parameters as well as the intensity ratio between both pulses making this torus-laser setup to an extraordinary candidate for light confinement, trapping and sensor applications.