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Title
Non-Hermitian and Nonlinear Physics in Exciton Polariton Condensates
Abstract
Exciton polaritons are hybrid light-matter quasiparticles that form due to strong light-matter coupling. Under nonresonant optical excitation, spontaneous macroscopic coherence can form, known as polariton condensation, pairing non-Hermiticity, with strong nonlinearity from polariton-polariton interactions. With the possibility to control gain and nonlinearity by optical means, this system allows for a comprehensive analysis of the interplay of nonlinearities, with topological properties and non-Hermiticity. Exceptional points (EPs) are singularities in the parameter space of non-Hermitian systems at which two or more eigenvalues and their corresponding eigenvectors coalesce. EPs have attracted considerable attention in a wide range of physical systems due to their intriguing spectral topology, with potential applications in sensing. We have investigated spectral topology and EPs in systems with significant nonlinearity, exemplified by a nonequilibrium exciton polariton condensate.
In this presentation, I will show that nonlinearity can induce a rotation of the Riemann surface and displacement of the EP. In nonlinear mode control, this offers interesting insights for phase transitions at EPs and encircling higher-order EPs. With potential applications in mind, I further demonstrate that sensing sensitivity near the EP can be significantly enhanced by nonlinearity. These results are generic enough to be applied to other non-Hermitian systems with similar nonlinearities such as in nonlinear optics and atomic systems, cf. Wingenbach et al., Phys. Rev. Research 6, 013148 (2024). I will also demonstrate the control of phase defects through polariton-polariton and spin-orbit interaction.
Bio
Jan Wingenbach is a visiting PhD student at the Wyant College of Optical Sciences. His research stay at the UofA is part of his PhD studies in the “Theory of Functional Photonic Structures” group led by Prof. Stefan Schumacher at the University of Paderborn, Germany. The group works on a broad range of topics in theoretical condensed matter physics, photonics, and quantum photonics. Recent topical interests include generation and tomography of few-photon states with solid state quantum-light sources, quantum coherence and quantum resource aspects of microcavity polariton condensates, non-Hermitian physics and topology in photonic systems, photophysics of organic and hybrid semiconductor materials, and development of efficient numerical algorithms for modern (high-performance) computing architectures. Besides their fundamental research interests, the group pursues active collaborations with various experimental partners and explores nonlinear light-matter interactions for novel light manipulations schemes, such as in optical switches and tunable quantum light sources. Prof. Schumacher also holds an adjunct appointment as Professor of Optical Sciences at the University of Arizona where he is currently spending his sabbatical, with Rolf Binder, Professor of Optical Sciences & Physics, being his local faculty host. Prof. Schumacher’s group is part of the interdisciplinary Institute for Photonic Quantum Systems (PhoQS) in Paderborn, Germany.