Fractional Quantum Hall Effect in the Second Landau Level of bilayer graphene

ORAL

Abstract

Bilayer graphene exhibits rich Quantum Hall physics due to valley, spin and orbital degrees of freedom that lead to a variety of polarization states. We study the Fractional Quantum Hall Effect (FQHE) in ultra-clean multiterminal bilayer graphene devices on boron nitride with a local graphite gate at magnetic fields of up to 45 T. We measure mobility of up to 1 million cm$^{\mathrm{2}}$/V.s and very low disorder. In addition to the broken-symmetry integer states, we unambiguously resolve a variety of fractions and focus on a series of fractions in the Second Landau Level, which do not follow particle-hole asymmetry. From the magnetic field dependence of the fractions, we find that some of these fractions have spin-polarized ground states while others are unpolarized, and we present a possible explanation for this difference. This work provides insights into how the symmetry-breaking electron-electron interactions and Zeeman splitting interact to produce a rich landscape of composite fermions in the Second Landau Level of bilayer graphene.

–

Authors

  • Georgi Diankov

    Stanford University

  • Francois Amet

    Stanford University

  • Menyoung Lee

    Stanford University, Department of Physics, Stanford University, Stanford, CA, 94305, USA

  • Andrew Bestwick

    Stanford University

  • Kevin Tharratt

    Department of Physics, Stanford University, Stanford, California 94305, USA, Stanford University

  • Chi-Te Liang

    Stanford University

  • David Goldhaber-Gordon

    Stanford University, Stanford Univ, Department of Physics, Stanford University, Stanford, CA, 94305, USA