  In recent years, exciton-polariton microcavity arrays have emerged as a
promising semiconductor-based platform for analogue simulations of model
Hamiltonians and topological effects. To realize experimentally a variety of
Hamiltonians and change their parameters, it is essential to have highly
tunable and easily engineerable structures. Here, we demonstrate in-situ
tunable, room-temperature polariton condensation in individual states of a
one-dimensional topological lattice, by utilizing an open-cavity configuration
with an organic polymer layer. Angle-resolved photoluminescence measurements
reveal the band structure of the Su-Schrieffer-Heeger chain, comprised of
S-like and P-like bands, along with the appearance of discrete topological edge
states with distinct symmetries. Changing the cavity length in combination with
vibron-mediated relaxation in the polymer allows us to achieve selective
polariton condensation into different states of the band structure, unveiled by
nonlinear emission, linewidth narrowing, energy blue-shift and extended
macroscopic coherence. Furthermore, we engineer the bandgap and the edge state
localization by adjusting the interaction between adjacent lattice sites.
Comparison to first-principles calculations showcases the precision of the
polariton simulator. These results demonstrate the versatility and accuracy of
the platform for the investigation of quantum fluids in complex potential
landscapes and topological effects at room temperature.
