Quantum Hall transport as a probe of capacitance profile at graphene edges

Vera‐Marun, Ivan J.; Zomer, P. J.; Veligura, A.; Guimarães, Marcos H. D.; Visser, L.; Tombros, N.; Elferen, H. J. van; Zeitler, U.; Wees, van Bart

doi:10.1063/1.4773589

Cited by 25 publications

(44 citation statements)

References 30 publications

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“…Enhanced conductance can also arise due to electric field focusing at the sample edges [39]. This effect may be particularly relevant for top gates deposited after etching, resulting in conformal coverage of the etched walls.…”

Section: Discussionmentioning

confidence: 99%

Edge transport in the trivial phase of InAs/GaSb

et al. 2016

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We present transport and scanning SQUID measurements on InAs/GaSb double quantum wells, a system predicted to be a two-dimensional topological insulator. Top and back gates allow independent control of density and band offset, allowing tuning from the trivial to the topological regime. In the trivial regime, bulk conductivity is quenched but transport persists along the edges, superficially resembling the predicted helical edge-channels in the topological regime. We characterize edge conduction in the trivial regime in a wide variety of sample geometries and measurement configurations, as a function of temperature, magnetic field, and edge length. Despite similarities to studies claiming measurements of helical edge channels, our characterization points to a nontopological origin for these observations.

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Section: Discussionmentioning

confidence: 99%

Edge transport in the trivial phase of InAs/GaSb

et al. 2016

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“…Therefore, we have to point out that the linear scaling will hold as well for a leverage factor of 1.1 × 10 10 cm −2 V −1 if we assume ν = 4 and 2 as the observed sequence of plateaus. From previous studies 29 we know that the capacitance probed by the quantum Hall effect (QHE) in graphene devices (especially in suspended samples) can be higher than the geometrical value, due to the deviation from the plane capacitor model. However, we attribute the observed plateaus to the filling factors 2 and 1.…”

Section: Temperature Dependence and Quantum Transportmentioning

confidence: 99%

Transport gap in suspended bilayer graphene at zero magnetic field

et al. 2012

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We report a change of three orders of magnitude in the resistance of a suspended bilayer graphene flake which varies from a few k in the high-carrier-density regime to several M around the charge neutrality point (CNP). The corresponding transport gap is 8 meV at 0.3 K. The sequence of quantum Hall plateaus appearing at filling factor ν = 2 followed by ν = 1 suggests that the observed gap is caused by the symmetry breaking of the lowest Landau level. Investigation of the gap in a tilted magnetic fields indicates that the resistance at the CNP shows a weak linear decrease for increasing total magnetic field. Those observations are in agreement with a spontaneous valley splitting at zero magnetic field followed by splitting of the spins originating from different valleys with increasing magnetic field. Both the transport gap and B field response point toward the spin-polarized layer-antiferromagnetic state as the ground state in the bilayer graphene sample. The observed nontrivial dependence of the gap value on the normal component of B suggests possible exchange mechanisms in the system.

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“…21 the increase in capacitance of the system under the applied magnetic field could be understood from the deviation from the flat-plate capacitor model. At the point when the width of the graphene flake is smaller or comparable to the distance to the back gate the flatplate capacitor model can no longer be applied.…”

Section: Appendixmentioning

confidence: 99%

“…The geometrical gate capacitance is given by a combination of the vacuum gap (1.15 μm) and SiO 2 substrate (0.5 μm). Using a serial capacitor model we calculate a gate capacitance of 7.2 aF/μm −2 which directly relates the carrier concentration to V G as n = α(V G − V CNP ) with leverage factor α = 0.5 × 10 14 m −2 V −1 and a finite voltage of the the CNP of V CNP = 1.2 V. In high magnetic fields, the geometric capacitance increases due to the formation of edge states 21 and α becomes dependent on B. Therefore, the exact values of capacitance were determined experimentally by identifying the filling factors of quantized Hall plateaus in magnetic field; details can be found in the appendix.…”

Section: Experimental Backgroundmentioning

confidence: 99%

Field-induced quantum Hall ferromagnetism in suspended bilayer graphene

et al. 2012

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Field-induced quantum Hall ferromagnetism in suspended bilayer graphene van Elferen, H. J.; Veligura, A.; Kurganova, E. V.; Zeitler, U.; Maan, J. C.; Tombros, N.; VeraMarun, I. J.; van Wees, B. J. We have measured the magnetoresistance of freely suspended high-mobility bilayer graphene. For magnetic fields B > 1 T we observe the opening of a field-induced gap at the charge neutrality point characterized by a diverging resistance. For higher fields the eightfold degenerated lowest Landau level lifts completely. Both the sequence of this symmetry breaking and the strong transition of the gap-size point to a ferromagnetic nature of the insulating phase developing at the charge neutrality point.

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Quantum Hall transport as a probe of capacitance profile at graphene edges

Cited by 25 publications

References 30 publications

Edge transport in the trivial phase of InAs/GaSb

Edge transport in the trivial phase of InAs/GaSb

Transport gap in suspended bilayer graphene at zero magnetic field

Field-induced quantum Hall ferromagnetism in suspended bilayer graphene

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