Fractional Quantum Hall States in Bilayer Graphene Probed by Transconductance Fluctuations

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Abstract
We have investigated fractional quantum Hall (QH) states in Bernal-stacked bilayer graphene using transconductance fluctuation measurements. A variety of odd-denominator fractional QH states with νQH → νQH + 2 symmetry, as previously reported, are observed. However, surprising is that also particle-hole symmetric states are clearly resolved in the same measurement set. We attribute their emergence to the reversal of orbital states in the octet level scheme induced by a strong local charge imbalance, which can be captured by the transconductance fluctuations. Also the even-denominator fractional QH state at filling −1/2 is observed. However, contrary to a previous study on a suspended graphene layer [Ki et al. Nano Lett. 2014, 14, 2135], the particle-hole symmetric state at filling 1/2 is detected as well. These observations suggest that the stability of both odd and even denominator fractional QH states is very sensitive to local transverse electric fields in bilayer graphene.
Funding Information
  • Ministerstvo ?kolstva, vedy, v?skumu a ?portu Slovenskej republiky (OPVaV-2011/4.2/01-PN)
  • Deutsche Forschungsgemeinschaft (SPP 1459)
  • Korea government (2011-0031558)
  • Korea Institute of Science and Technology
  • National Research Foundation of Korea (2011-0030785, NRF-2012M3C1a1048861)
  • IBS (IBSR014-D1-2014-a02)
  • Max-Planck-Gesellschaft (2011-0031558)

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