Unveiling magnetoplasmon polaritons in graphene with THz s-SNOM in extreme conditions

Abstract

In the last decade, we have witnessed the dominance of graphene plasmonics in the nanophotonic realm. Unlike plasmons in noble metals, graphene plasmons can be confined with splendid tunability from the Terahertz (THz) to the mid-infrared (mid-IR). Moreover, by applying magnetic fields to graphene, cyclotron resonances may couple to the collective charges motion, giving rise to magnetoplamons (MP). These novel quasi-particles have been indirectly observed in graphene by THz far-field techniques but never imaged in real space. Nano-imaging could be performed by scattering-type Scanning Near-field Optical Microscopy (s-SNOM). However, adding the THz spectrum to this instrument with fine control of environmental conditions, such as temperature and magnetic fields, is a challenge that is faced by the community. This proposal aims to investigate surface MP polaritons (SMPPs) in graphene with a state-of-the-art s-SNOM. The project is a collaboration between the Imbuia group (infrared beamline) at the Brazilian Synchrotron Light Laboratory (LNLS - Sirius) and Mengkun Liu's group at Stony Brook University (U.S.A.). Prof. Liu is an experienced researcher who has been broadening the scope of s-SNOM by operating it in cryogenic temperatures and high magnetic fields (magnetic cryo-SNOM) and implementing it with THz Time-Domain Spectroscopy (TDS-SNOM). The first part of the study will be carried out in Brazil, where the student will fabricate the graphene device for electrical characterization. In the Research Internship Abroad (BEPE), the student, under Prof. Liu's supervision, will assist coupling the THz TDS system to the magnetic cryo-SNOM and then, with the adapted instrumentation, investigate SMPPs in graphene. We believe that the project will not only bring relevant advances in the nano-optics research of quantum materials but also furnish the student with substantial foundations in THz and cryogenic technologies. (AU)