Tunable magneto-plasmons in graphene: an infrared study

Plasmons, collective oscillations of electrons, in graphene have attracted much attention due to their important roles in understanding the intriguing physics of graphene and potential applications in optoelectronic devices. Using infrared spectroscopy, we investigated the optical response of the plasmons in micrometer-sized graphene disks in high magnetic fields up to 18 T. Our study shows that the plasmon resonance splits into edge and bulk modes in magnetic fields. Due to the linear band structure of graphene, the splitting exhibits a sensitive doping dependence, which is not observed in conventional two-dimensional electron gas systems. Moreover, the lifetime of the two modes can be dramatically modified by magnetic fields, with the edge plasmons developing increasingly longer lifetimes in high fields. The latter behavior can be understood from the suppression of backscattering at the edges. Our work not only opens an avenue to explore the magneto-plasmons and edge physics in graphene but also supports the great potential of graphene for tunable magneto-optical devices.\\[4pt] [1] Hugen Yan, Zhiqiang Li, Xuesong Li, Wenjuan Zhu, Phaedon Avouris, and Fengnian Xia, Nano letters, 12, 3766 (2012).