We theoretically investigate the effect of symmetry breaking on the ultrafast plasmon responses of Au nanodisk(ND)dimers by varying the diameter of one of the constituent nanodisks.In the case of a single ultrafast laser pulse,we demon-strate that the ultrafast responses of Au ND homodimer can be significantly modified due to the effect of symmetry breaking.The symmetric dimer shows a single broad spectral peak,whereas the size-asymmetric dimer shows three spectral peaks.The first system displays at most one temporal maximum and no beats in ultrafast temporal,whereas the second system may have three temporal maxima and two beats due to a combination of broken symmetry and the coherent superposition between various plasmon modes induced by the ultra-short laser pulse.Moreover,the shape of temporal dynamics of the size-asymmetric dimer is significantly deformed due to the excitation of local plasmon modes with different wavelength components.Furthermore,the decay time of the amplitude of the local field is longer and oscillates with a high frequency due to the narrower linewidth and red-shifted spectral peaks.We show that the ultrafast plasmon responses of both dimers can be controlled by varying the relative phase and time delays between a pair of two pulses.Our results will open new paths to understanding ultrafast plasmon responses in asymmetric heterodimers with suitable properties for different applications.

School of Science,Changchun University of Science and Technology,Changchun 130022,China;Department of Physics,College of Natural and Computational Sciences,Wolaita Sodo University,P.O.Box 138,Wlaita Sodo,Ethiopia

[1]Bereket Dalga Dana;Alemayehu Nana Koya;Xiaowei Song;Jingquan Lin-.Ultrafast plasmon dynamics in asymmetric gold nanodimers)[J].中国物理B（英文版）,2022(06):436-444

nanodimers,homodimer,heterodimers

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