Abstract Submitted for the MAR14 Meeting of The American Physical Society Insulator-quantum Hall transition and Dirac fermion heating in low-carrier-density monolayer epitaxial graphene

Submitted for the MAR14 Meeting of The American Physical Society Insulator-quantum Hall transition and Dirac fermion heating in low-carrier-density monolayer epitaxial graphene LUNG-I HUANG1, YANFEI YANG2, RANDOLPH ELMQUIST, DAVID NEWELL, National Instutute of Standards and Technology, CHI-TE LIANG, National Taiwan University — We present magneto-transport measurements on ungated, low-carrier-density epitaxial graphene Hall devices at low temperatures T . At T =4.25 K the carrier density and mobility of one device are 1.38x1011 cm−2 and 6500 cm2V−1s−1, respectively. At low magnetic fields B, this device shows insulating behavior in the sense that the measured resistivity ρxx increases with decreasing T . A highly developed quantum Hall (QH) resistivity plateau ρxy ≈ h 2e2 corresponding to a Landau-level filling factor ν =2 in monolayer graphene can be observed at magnetic fields B ≥ 1.5 T. Between the low-field insulator regime and the ν =2 QH state we observe a T -independent point in ρxx which corresponds to the insulator-quantum Hall (I-QH) transition. This transition, like those in semiconductor-based two-dimensional (2D) systems, can be also observed by increasing the driving current I at fixed ambient temperature. However, the measured ρxx at the I-QH transition is close to h 4e2 , rather than h 2e2 as expected by conventional I-QH theory. Furthermore, ρxx is substantially higher than ρxy at the crossing point. By using the zero-field resistivity and weak localization effect as two independent thermometers to determine effective Dirac fermion temperature (TDF ) at various I, we find that TDF ∼ I0.5, consistent with those obtained in various 2D systems. 1NIST and National Taiwan University 2NIST and Georgetown University Randolph Elmquist NIST Natl Inst of Stds & Tech Date submitted: 09 Jan 2014 Electronic form version 1.4