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- Nachawaty, A., et al.
(författare)
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Magnetic field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point
- 2017
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 96:7
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the disorder of epitaxial graphene close to the charge neutrality point (CNP) by various methods: (i) at room temperature, by analyzing the dependence of the resistivity on the Hall coefficient; (ii) by fitting the temperature dependence of the Hall coefficient down to liquid helium temperature; (iii) by fitting the magnetoresistances at low temperature. All methods converge to give a disorder amplitude of (20 +/- 10) meV. Because of this relatively low disorder, close to the CNP, at low temperature, the sample resistivity does not exhibit the standard value similar or equal to h/4e(2) but diverges. Moreover, themagnetoresistance curves have a unique ambipolar behavior, which has been systematically observed for all studied samples. This is a signature of both asymmetry in the density of states and in-plane charge transfer. Themicroscopic origin of this behavior cannot be unambiguously determined. However, we propose a model in which the SiC substrate steps qualitatively explain the ambipolar behavior.
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| 2. |
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| 3. |
- Yang, M., et al.
(författare)
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Puddle-Induced Resistance Oscillations in the Breakdown of the Graphene Quantum Hall Effect
- 2016
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 117:23
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Tidskriftsartikel (refereegranskat)abstract
- We report on the stability of the quantum Hall plateau in wide Hall bars made from a chemically gated graphene film grown on SiC. The v = 2 quantized plateau appears from fields B similar or equal to 5 T and persists up to B similar or equal to 80 T. At high current density, in the breakdown regime, the longitudinal resistance oscillates with a 1/B periodicity and an anomalous phase, which we relate to the presence of additional electron reservoirs. The high field experimental data suggest that these reservoirs induce a continuous increase of the carrier density up to the highest available magnetic field, thus enlarging the quantum plateaus. These in-plane inhomogeneities, in the form of high carrier density graphene pockets, modulate the quantum Hall effect breakdown and decrease the breakdown current.
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