title: Physics. Creating and probing electron whispering-gallery modes in graphene.
abstract: The design of high-finesse resonant cavities for electronic waves faces challenges due to short electron coherence lengths in solids. Complementing previous approaches to confine electronic waves by carefully positioned adatoms at clean metallic surfaces, we demonstrate an approach inspired by the peculiar acoustic phenomena in whispering galleries. Taking advantage of graphene's gate-tunable light-like carriers, we create whispering-gallery mode (WGM) resonators defined by circular pn junctions, induced by a scanning tunneling probe. We can tune the resonator size and the carrier concentration under the probe in a back-gated graphene device over a wide range. The WGM-type confinement and associated resonances are a new addition to the quantum electron-optics toolbox, paving the way to develop electronic lenses and resonators.
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. Maryland NanoCenter, University of Maryland, College Park, MD 20742, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Wyrick
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Fabian D
authors.initials: FD
authors.lastname: Natterer
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Joaquin F
authors.initials: JF
authors.lastname: Rodriguez-Nieva
authors.affiliation: Department of Physics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Cyprian
authors.initials: C
authors.lastname: Lewandowski
authors.affiliation: National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Leonid S
authors.initials: LS
authors.lastname: Levitov
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. nikolai.zhitenev@nist.gov joseph.stroscio@nist.gov.
authors.forename: Nikolai B
authors.initials: NB
authors.lastname: Zhitenev
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. nikolai.zhitenev@nist.gov joseph.stroscio@nist.gov.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Stroscio