Engineering non-Hermitian Hamiltonians in nonlinear exciton-polariton systems

• Applicant: Dr. Xuekai Ma
• Subject Area: Theoretical Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467358803

Non-Hermitian Hamiltonians have sparked great interest and have been intensively investigated in various physical systems. Many exotic properties have been reported in non-Hermitian optics in microstructures, including microcavity polaritons which are light-matter hybrid quasiparticles composed of excitons and photons, with a particular focus on their potential applications in manipulating photons and customizing light. In this project, we will focus on engineering non-Hermitian Hamiltonians in polariton systems, which are intrinsically dissipative and show rich physics including strong nonlinearity. The main objectives of the present project include: (i) Investigating topological properties mediated by different types of optical spin-orbit couplings (SOCs). For example, the SOC can give rise to non-Hermitian exceptional rings, and the ring may be broken by other physical properties such as nonlinearity or inhomogeneity, resulting in nontrivial topology and complex Riemann surfaces and consequently enabling unprecedented mode manipulation; (ii) Exploring novel nonlinear phenomena around the bound states in the continuum (BICs). One expected interesting nonlinear phenomenon is the vortex formation without trapping potentials which is related to the intrinsic nature of the polarization vortices around the BICs and SOC; (iii) Constructing non-Hermitian skin effect in designed lattices. An interesting structure is the double-wave lattice that we developed in the Hermitian case and which support topological insulator states. The coexistence of the skin effect and topological insulators in the same structure may spark new physics. Overall, by carrying out the current project, new theoretical models and concepts will be developed for polariton systems and non-Hermitian physics with nonlinearity. The expected outcomes and theoretical insights would have a broad impact on the study of nonlinear optics, many-body physics, and topological photonics. Beyond fundamental physics, the expected results would be conductive to developing functional photoelectric as well as photonic devices and sensors.

• DFG Programme: Research Grants
• International Connection: China
• Co-Investigator: Professor Dr. Stefan Schumacher
• Cooperation Partner: Professor Henry Fu