Fig. 4: Photoluminescence and propagation of MoSe₂ TPs.

Angle-resolved photoluminescence maps for TM-(a) and TE-(b) polarized collection in logarithmic scale. The sample is excited non-resonantly with CW laser at ~1.96 eV. For better visibility, regions of lower and upper polariton branches are plotted in different color scales. Dispersion of the modes extracted from fitting the PL data with coupled oscillator model are marked with lines: uncoupled photonic mode (dashed white), uncoupled exciton (dashed green) and the resulting polariton branches (solid white). c Left: angle-resolved differential reflectivity map for σ⁻ -polarized light compared to the calculation of photonic and excitonic fractions in the modes via TBM model. Right: real-space maps demonstrating one-way propagation of polaritonic edge states. The maps show the differential images of the sample excited with focused σ⁺ and σ⁻ -polarized laser pulses with a linewidth of ~10 meV. The calculated exciton fractions for the shown frequencies are 0.05 (1.72 eV), 0.11(1.7 eV), and 1 (1.65 eV, the exciton frequency). Scale bars are each 10 µm. Horizontal black dashed lines enframe the beam stop that blocked the directly reflected light. Vertical dashed lines represent the position of the domain wall.