Silizium-Nanokristalle für optoelektronische Anwendungen

In dieser Arbeit wird die Herstellung erster siliziumbasierter Leuchtdioden (SiLEDs) auf Basis von Silizium-Nanokristallen demonstriert. In einer detaillierten Studie werden zudem die optoelektronischen und morphologischen Eigenschaften der SiLEDs eingehend untersucht. Weitere Anwendungsgebiete der Silizium-Nanokristalle von der Biomedizin bis hin zum Lasersintern der Partikel sowie eine umfassende spektroskopische Untersuchung dieses neuartigen Nanomaterials runden diese Arbeit ab

Exchange-enhanced Ultrastrong Magnon-Magnon Coupling in a Compensated Ferrimagnet

The ultrastrong coupling of (quasi-)particles has gained considerable attention due to its application potential and richness of the underlying physics. Coupling phenomena arising due to electromagnetic interactions are well explored. In magnetically ordered systems, the quantum-mechanical exchange-interaction should furthermore enable a fundamentally different coupling mechanism. Here, we report the observation of ultrastrong intralayer exchange-enhanced magnon-magnon coupling in a compensated ferrimagnet. We experimentally study the spin dynamics in a gadolinium iron garnet single crystal using broadband ferromagnetic resonance. Close to the ferrimagnetic compensation temperature, we observe ultrastrong coupling of clockwise and anticlockwise magnon modes. The magnon-magnon coupling strength reaches more than 30% of the mode frequency and can be tuned by varying the direction of the external magnetic field. We theoretically explain the observed phenomenon in terms of an exchange-enhanced mode-coupling mediated by a weak cubic anisotropy