Recently, the International Center for Quantum Design of Functional Materials of the National Research Center for Microscale Matter Sciences of the University of Science and Technology of China in Hefei, the School of Physics, the Key Laboratory of Strongly Coupled Quantum Materials Physics of the Chinese Academy of Sciences, Professor Zeng Changgan's group, and the research group of researcher Li Xiaoguang of Shenzhen University have made important progress in the experimental and theoretical cooperation in the regulation of plasmonic attenuation of graphene coupling. By adjusting the Fermi level of graphene, an additional attenuation channel is designed and introduced, which realizes the remote control of the coupling plasmon lifetime, and elucidates the attenuation control mechanism by combining the theory. The results were published Nov. 30 in the journal Physical Review Letters under the headline "Electric Field-Controlled Damping Switches of Coupled Dirac Plasmons," It was selected as Editors' Suggestion by the editorial board of the journal.

Quasiparticles are one of the most important basic concepts in condensed matter physics. The interaction between light and matter can form quasiparticles such as plasmon, exciton, phonon polaron, etc. These quasiparticles show rich physical properties and broad application prospects, such as plasmon metamaterials, exciton-color Einstein condensation, nanophonon resonators, etc. The lifetime is a key parameter of these quasiparticles, and the appropriate lifetime is the premise of whether the rich physical properties of quasiparticles can be detected and converted into practical applications. Therefore, a great deal of research work has focused on exploring the decay mechanism of quasiparticles and finding systems with intrinsic suitable lifetimes. Another important research direction is to explore the active control method of quasiparticle lifetime, which will provide a new starting point for the research and application of quasi-particle correlation systems.

Professor Zeng Changgan's research team has been committed to studying the quantum regulatory behavior of quasiparticle systems, especially plasmon systems. In the previous work, it was found that electron-plasmon coupling has a great enhancement effect on the quantum coherence of graphene electron transport (Phys. Rev. Lett. 119, 156803 (2017)). Quantum regulation of plasmon excitation and propagation is realized by using a tunable step barrier (Nano Lett. 18, 1373 (2018)).

Recently, in collaboration with Professor Zeng Changgan's research team and Professor Li Xiaoguang's research group at Shenzhen University, a systematic study of coupled Dirac plasmon in graphene/boron nitride/graphene structures has been carried out by combining scattering scanning near-field optical microscopy and random phase approximation theoretical calculation methods, and multi-dimensional regulation of coupled plasmon has been realized. Due to the Coulomb interaction, the plasmons of the two layers of graphene form an optical coupling mode with longer wavelength and higher intensity through long-range coupling. By changing the graphene carrier concentration and interlayer spacing and other parameters, the wavelength and intensity can be greatly adjusted. More importantly, the lifetime of the coupled plasmon can be remotely regulated by an electric-field-controlled attenuation channel. Using the Dirac linear dispersion of graphene, the team designed one of the layers as a attenuation modulator, which opened and closed the attenuation channel by changing its Fermi level, thus achieving active control of the quastiparticle lifetime. This work designs a prototype device for nanophotonics and provides a new idea for active control of other quasiparticle lifetimes.

Note: Schematic diagram of graphene coupled plasmon (FIG. a), attenuation regulation of coupled plasmon by carrier concentration regulation (FIG. b), attenuation regulation mechanism and attenuation switch (FIG. c,d)



Huayang Zhang, PhD candidate in the Department of Physics, and Xiaodong Fan, special Associate Researcher in the Department of Physics, are co-first authors of the paper, and Professor Changgan Zeng, Professor Xiaoguang Li and Special Associate Researcher Xiaodong Fan are co-corresponding authors. The research was funded by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Chinese Academy of Sciences and Anhui Province.

Article link:https://link.aps.org/doi/10.1103/PhysRevLett.129.237402

(Hefei National Research Center for Microscale Matter Science, School of Physics, Institute of Quantum Information and Quantum Technology Innovation, Chinese Academy of Sciences, Department of Scientific Research)