Plasmon coupling behavior in aluminium nanoparticle arrangements

Controlling and optimizing the optical response of complex nanoparticle arrangements are important for a rational design of plasmonic nanostructures. Using time dependent density functional theory calculations, we present a systematic study of the plasmon coupling behavior in Al nanoparticles organized in a chain and a square arrangement as a function of the interparticle distance in the range of 3 to 14 A. The chain arrangement shows a progressive redshifting of the gap plasmon and a systematic spectral weight reduction with the decreasing interparticle distance in the range of 6 to 14 A. As the interparticle distance is further reduced to 5 A, there is a redshift-to-blueshift crossover due to the onset of quantum tunneling and the gap plasmon is replaced by a charge-transfer plasmon. In contrast, the square arrangement exhibits non-systematic changes in the spectral shifting and spectral weights with the decreasing interparticle distance in the range of 6 to 14 A due to the complex multiple plasmon coupling. Interestingly, spectral blueshifting begins from 5 A similar to the chain case. We believe that this theoretical study might be useful for the design of Al plasmonic nanostructures.