Selective organic polariton condensation in individual states of a 1D topological lattice

Abstract

Arrays of coupled exciton-polariton condensates have recently emerged as a promising semiconductor-based platform for analogue quantum simulations. However, the traditionally utilized monolithic cavity configurations significantly limit the possible range of tuning and control. Here, we use a wavelength-tunable cavity with an organic active layer to demonstrate room temperature, selective condensation of polaritons in individual states of a one dimensional (1D) topological lattice. The investigated lattice is comprised of adjacent sites with alternating bond strength, a so called Su-Schrieffer–Heeger (SSH) chain. First, we perform below threshold, angle-resolved photoluminescence measurements to populate the lattice’s bandstructure. Locally exciting the center of the structure reveals a bandstructure comprised of S-like and P-like energy bands. Repeating the measurement at the edge of the structure leads to the observation of a discrete topological edge state which appears inside the first energy gap. Next, we drive the system above condensation threshold. Using the tunability of our cavity and a vibron assisted relaxation mechanism, unique to organic materials, we can selectively condense polaritons to individual states of the 1D topological lattice (Fig. 1). Using a Michelson interferometer we investigate the coherence of the condensates, which spatially extends through almost the whole structure. Finally, we showcase engineering of the energy gap and of the topological edge state localization by tuning the coupling strength within the subunits of the SSH chain. These results showcase the potential of our highly engineerable and tunable platform for the study of topological effects and complex potential landscapes at room temperature.