Fig. 2
From: Valley coherent exciton-polaritons in a monolayer semiconductor
Strong exciton-photon coupling in WSe2 monolayers. a Schematic of a WSe2 monolayer placed in an open hemispherical 0-dimensional microcavity, maintained at 4.2 K in a LHe bath cryostat with superconducting magnet. Piezo nanopositioners allow tuning of cavity length. b Photoluminescence spectra measured as the cavity mode is scanned across the exciton resonance, showing the formation of the lower and upper polariton branches, LPB and UPB, respectively. Blue (green) dashed curves guide the approximate peak positions of the LPB (UPB). c Extracted polariton peak positions as a function of the exciton-photon detuning. Ec (dotted line) is the energy of the tunable cavity mode. Dashed lines are the energies of the exciton and trion. The green (blue) symbols show spectral positions of the UPB (LPB) peaks. The red lines correspond to a coupled oscillator model fit with a Rabi splitting of 26.2 ± 0.1 meV. d Spectra corresponding to tuning the ground state mode through the trion energy, demonstrating weak coupling between the cavity and trion. Blue (red) dashed line indicates the energy of the trion (cavity mode)
