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Dr. Florian Dirnberger , Department of Physics, City College of New York, USA

Strongly correlated excitons & exciton-polaritons in van der Waals magnetic crystals

07.06.2022 (Tuesday) , 15:15
Hermann-Krone-Bau, Lecture Hall KRO 1.11 , Nöthnitzer Straße 61 , 01187 Dresden

The revolutionary impact of graphene and single layer transition-metal dichalcogenides on solid-state
physics has led to a quest for materials with novel optical, electronic and magnetic properties. As a result of
this process, more and more van der Waals materials characterized by a collective behavior of their electronic
constituents have made an appearance on the center of the stage of solid-state research. So far, these
quantum materials encompass correlated insulators, topological insulators, and superconductors, as well
as a fascinatingly broad palette of ferroelectric, multiferroic, and magnetic crystals.
Optical spectroscopy studies of these materials recently discovered excitons that are deeply intertwined
with a collective quantum state. With properties that have no analog amongst excitons in conventional
band semiconductors, these excitons not only inherit a tremendous potential for the design of novel
optoelectronic devices, but also represent an exciting material platform to uncover new facets of light-matter
interactions. In this talk, I will introduce two different types of van der Waals antiferromagnetic crystals
reported to date to host such strongly correlated excitons: the correlated insulator NiPS3 and the magnetic
semiconductor CrSBr.
I will then focus on our recent study on strong light-matter coupling in NiPS3, a magnetic crystal
with antiferromagnetic zig-zag spin ordering below the Néel temperature. In this material, a previously unobserved
class of polaritonic quasiparticles emerges from the strong coupling between its spin-correlated
excitons and the photons inside a microcavity. I will show how hybridization with light offers unique opportunities
to study the nature of novel magnetically coupled excitations in antiferromagnetic insulators and
present our microscopic understanding of these spin-correlated excitons. By establishing strong coupling
between photons and correlated optical excitations in a magnetic crystal, our work introduces van der Waals
quantum materials to the field of strong light-matter physics and provides a path towards the design and
control of correlated quantum states via cavity quantum electrodynamics.

Florian Dirnberger received his Ph.D. from the University of Regensburg (Germany) for his work on
exciton- and spin phenomena in semiconductor nanowires. After receiving a Walter-Benjamin post-doc fellowship
from the German Research Foundation, he joined the group of Prof. Vinod M. Menon at the City
College of New York in 2019 to study optical phenomena in 2D materials. His current research is focused on
novel interactions between light and matter in magnetic van der Waals crystals.


Host: Prof. Alexey Chernikov

Everybody welcome!

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