SciPost Thesis Link
| Title: | Quantum Metric and Topology in the exploration of photonic Dirac systems | |
| Author: | Charly Leblanc | |
| As Contributor: | Charly Leblanc | |
| Type: | Ph.D. | |
| Field: | Physics | |
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| Approaches: | Theoretical, Experimental, Computational | |
| URL: | https://theses.hal.science/tel-03975344 | |
| Degree granting institution: | Université Clermont Auvergne | |
| Supervisor(s): | Dmitry Solnyshkov, Guillaume Malpuech | |
| Defense date: | 2022-10-14 |
Abstract:
This thesis is dedicated to the study of photonic Dirac systems, the role of their associated topology and Quantum Metric, and their behavior with respect to non-Hermiticity.After introductory chapters on these subjects, we first study Dirac points in microcavi- ties. By exciting coherently two bands near a Dirac point, we experimentally demonstrate Zitterbewegung oscillations from a polariton wavepacket. The dynamics can be fully under- stood thanks to a non-Abelian Yang-Mills theory, which couple the precession of the spin to the spatial dynamics.Then we introduce a previous work, describing the photonic anomalous Hall effect in the opposite regime, when a single band is excited adiabatically. Afterwards, we demonstrate that both of these regime can be described in a single formalism, taking the form of semiclas- sical equations using only static band parameters, namely the dispersion and the Quantum Metric.Following this, we present an experimental work about a spin-selective strong light-matter coupling regime which results in unusually strong optical nonlinearity and a giant Zeeman effect, which allows to open a gap at the Dirac point in polaritonic systems, and which has direct applications in topological physics.In the last chapter, we demonstrate that in presence of non-Hermiticity, a Dirac point will transform into a pair of exceptional points, linked by a Fermi arc. We show theoretically that the Quantum Metric diverges at the vicinity of an exceptional point. This divergence allows to understand the complex behavior of a wavepacket centered at this point.Lastly, we present the first experimental extraction of the Quantum Metric in a non- Hermitian system, exhibiting exceptional points. This thesis ends with the observation of the divergence of the Quantum Metric at the vicinity of exceptional points, accordingly with the theory.