Fig. 2: Excess energy and polaronic nature of the IX emission.

a False color plot of the IX PL spectra for a series of excitation energies E_ex. Horizontal gray dashed lines correspond to the resonant excitation of MoSe₂ and WSe₂ intralayer excitons. b Selected IX PL spectra of the 3R−(top) and 2H−(bottom) samples, plotted on an energy scale relative to the local minima of the spectra in between the emission lobes. The N = 0 peak is at  ~1.305 eV and  ~1.380 eV for the 3R and the 2H sample, respectively). Spectra in green correspond to the IX emission obtained by exciting the sample just below the intralayer exciton of WSe₂ at E_ex = 1.653 eV(1.687 eV) for the 3R−(2H−) sample (green dotted lines in a) and the blue spectra are excited just above the resonance, at E_ex = 1.685 eV(1.720 eV) for the 3R − (2H − ) sample (blue dotted lines in (a). Vertical dotted lines mark the position of the sharp PL features. Black arrows mark the position of peaks that were not discernible. c Peak energy as function of peak number for the 3R−(top) and the 2H−(bottom) sample. The peaks are uniformly spaced with an energy interval of  ~0.8 meV. Energy error bars are below the dot size.