Fig. 1. (a) Diagram of surface plasmon cavity optomechanical system driven by a strong pump laser and probed by a weak signal laser. The double molecules reside on the substrate. (b) Molecules of thiophenol and GBT in their lowest energy conformations. (c) Interacting molecules with R the intermolecular distance, and x1 and x2 the distances between different charges for the instantaneous dipoles.

Fig. 2. (a) Transmission spectrum of the probe beam as a function of the probe–pump detuning with different van der Waals coupling rates for the same molecules (GBT). We choose λ=0,0.2, and 0.4  THz; and Δp=0. The other parameters are Ωpu2=0.22  eV2, ω1=ω2=32.2  THz, g1=g2=70  GHz, κ/(2π)=33  THz, and γ1,2/(2π)=0.06  THz. (b) Energy levels of the coupled system corresponding to the transmission peak shift. (c) Linear relationship between frequency shift and coupling rate.

Fig. 3. (a) Transmission spectrum of the probe beam as a function of the probe–pump detuning with various van der Waals coupling rates for different two molecules (thiophenol and GBT). We choose λ=0,0.1,and 0.4  THz; Δp=0; Ωpu2=0.22  eV2; and ω1=32.1  THz, ω2=32.2  THz, g1=4.7  GHz, g2=70  GHz, κ/(2π)=33  THz, γ1,2/(2π)=0.06  THz. (b) Energy levels of the coupled system corresponding to the enhanced peak splitting. (c) Linear relationship between split distance D and coupling rate λ.

Fig. 4. Transmission and reflection spectrum of a signal beam with different range between molecules (thiophenol and GBT) in the case of Ωpu2=0.09  eV2. Other parameters are same with Fig. 2.