Figure 3.

The calculated STML of a TPP molecule coupled to a single plasmon mode is shown as a function of photon energy for four plexcitonic coupling strengths $\hslash g_{00}$ = 0 meV, 10 meV, 20 meV, and 30 meV at three bias voltages V_b = 1.8 V, 1.9 V, and 2.5 V. In the decoupled cavity limit ($\hslash g_{00}=0$ meV), the molecular vibrational spectrum is recovered. As g₁₁ is increased plexcitonic states begin to  form, giving rise to the characteristic split peak structure  in the EL. Although all radiative transitions have non-zero coupling to the plasmonic field, the resonant Q(0,0) transition dominates and the plexcitonic splitting is $\sim 2\hslash g_{00}$. The coherent mixing of multiple states gives rise to the asymmetric peak structure and the above threshold hot HL observed when V_b = 1.8 V; even for junctions operating in the weak coupling regime. For this system, the strong coupling boundary is $\hslash g_{00}>\sim$ 15 meV. Calculations are for junctions operating at T = 80 K, to be consistent with measured STML spectra¹⁸.