Mach-Zehnder interferometry using broken symmetry quantum Hall edges in graphene

ORAL

Abstract

Graphene has emerged as a unique platform for studying electron optics, particularly in the presence of a magnetic field. Here, we engineer a Mach-Zehnder interferometer using quantum Hall edge states that co-propagate along a single gate-defined NP interface. We use encapsulated monolayer graphene, clean enough to lift the four-fold spin and valley degeneracy. In order to create two separate co-propagating paths, we exploit the suppression of edge state scattering along gate defined edges, and use scattering sites at the ends of the NP interface to form our beam splitters. We observe conductance oscillations as a function of magnetic and electric field indicative of coherent transport, and measure values consistent with spin-selective scattering. We can tune our interferometer to regimes of high visibility ($>$98$\%$), surpassing the values reported for GaAs quantum-well Mach-Zehnder interferometers. These results demonstrate a promising method to observe interference between fractional charges in graphene.

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Authors

  • Di Wei

    Harvard University

  • Toeno van der Sar

    Harvard University, Department of Physics, Harvard University

  • Javier Sanchez-Yamagishi

    Harvard University

  • Kenji Watanabe

    National Institute for Materials Science

  • Takashi Taniguchi

    National Institute for Materials Science

  • Pablo Jarrilo-Herrero

    Massachusetts Institute of Technology, USA, Massachusetts Institute of Thechnology, Massachusetts Inst of Tech-MIT, Massachusetts Institute of Technology, MIT

  • Bertrand Halperin

    Harvard University

  • A. Yacoby

    Harvard University, Harvard University, Cambridge USA., Department of Physics, Harvard University, Department of Physics, Harvard University, Cambridge, MA, 02138, Department of Physics, Harvard University, Cambridge, MA 02138