Experimental Evidence of Giant Non-reciprocity of WGM Modes in Graphene

Klein scattering in a circular graphene pn junction can lead to Whispering Gallery Mode(WGM) type resonances[1]. Utilizing the electrostatic potential induced by the probe of a scanning tunneling microscope, we create graphene electron resonators defined by circular pn junctions. These quasi-confined WGM states can be probed by tunneling spectroscopy measurements. With small applied magnetic fields, we observe a large energy splitting of the WGM states, displaying a manifestation of non-reciprocity due to Klein scattering of massless Dirac fermions in graphene~[2]. \begin{enumerate} \item Y. Zhao, et. al., \textit{Science }348(6235), 672-675 \item J. F. Rodriguez-Nieva, L. S. Levitov,\textit{ arXiv: 150806609} \end{enumerate}