Insulator-quantum Hall transition in monolayer epitaxial graphene

摘要

We report on magneto-transport measurements on low-density, large-area monolayer epitaxial graphene devices grown on SiC. We observe temperature ( T )-independent crossing points in the longitudinal resistivity ρ _(xx) , which are signatures of the insulator-quantum Hall (I-QH) transition, in all three devices. Upon converting the raw data into longitudinal and Hall conductivities σ _( xx ) and σ _( xy ) , in the most disordered device, we observed a T -driven flow diagram approximated by the semi-circle law as well as the T -independent point in σ _( xy ) near e ~(2) / h . We discuss our experimental results in the context of the evolution of the zero-energy Landau level at low magnetic fields B . We also compare the observed strongly insulating behaviour with metallic behaviour and the absence of the I-QH transition in graphene on SiO _(2) prepared by mechanical exfoliation.