WP1 –KPZ physics;
We conduct a combined theoretical and experimental investigation of polariton condensates to identify universality classes and explore phase diagrams as functions of noise, drive, nonlinearity, and reservoir fluctuations. Stochastic simulations of the Gross-Pitaevskii equation, in collaboration with Grenoble (Léonie Cannet, Anna Minguzzi), revealed complex 1D and 2D phase diagrams. In 1D, KPZ scaling regions, vortex nucleation, soliton formation, and reservoir-dominated regimes were identified (F. Vercesi et al., Phys. Rev. Research 5, 043062, 2023). In 2D, simulations show crossovers between BKT, KPZ, and Edward-Wilkinson regimes (F. Helluin et al., Phys. Rev. Research 7, 033103, 2025).
Experimentally, extended 2D condensates were realized, and first-order spatio-temporal coherence measured via interferometry. KPZ scaling was confirmed in both spatial and temporal decays. Reducing exciton content revealed a crossover to a diffusive Edward-Wilkinson regime. This provides access to critical exponents and universal scaling functions, a key milestone for the community.
WP2 – Nonlinear topology:
We investigate exotic nonlinear steady states and topology in driven-dissipative Kerr resonator arrays. A 1D Thouless pump is predicted through adiabatic modulation of the drive. Kerr nonlinearity modulates onsite energies, generating 1+1D Harper-Hofstadter bands with nonzero Chern numbers. Quantized Wannier-state motion demonstrates the emergence of topology from the interplay of drive and nonlinearity (S. Ravets et al., Phys. Rev. Lett. 134, 093801, 2025).
Helical bistability, an exotic solitonic response in coupled nonlinear resonators under phase-engineered drives, shows abrupt transitions between distinct nonlinear regimes and involves non-linear topological transitions. Experiments are ongoing with promising preliminary results.
Optical interferometry techniques were developed to measure topological invariants in 2D polariton lattices. Bloch eigenstates are measured, Berry curvature mapped, and Chern numbers computed in linear regimes (M. Guillot et al., arXiv:2507.16446). These results will be extended to Bogoliubov excitations.
WP3 – Quantum magnetism:
Quadratic pumping of polariton lattices was implemented on single micropillars, demonstrating two-photon absorption, emission of polariton pairs, and superbunching in second-order correlations. This protocol will be scaled to larger lattices to study quantum phases of light.
