Graphene p n junction in a quantizing magnetic field: Conductance at intermediate disorder strength

The transport properties of Chern insulator junctions generated by bipolar junctions in quantum Hall graphene are theoretically studied in the coherent regime. Coherent transport across the junction exhibits two mesoscopic features: valley-isospin dependence of the quantum Hall conductance, and the Aharonov-Bohm (AB) effects with the interface channels. We demonstrate that the valley-isospin dependence can be measured in a graphene sample with perfect edge terminations, resulting in conductance oscillation for the smallest Chern number case. On the other hand, while conductance plateaus are found to be unclear for larger Chern numbers, the conductance exhibits an oscillatory behavior of which period is relatively longer than the valley-isospin dependent oscillation. This conductance oscillation is ascribed to the AB effect, which is implicitly created by the split metallic channels near the junction interface. We point out that a possible origin of the unclear plateaus previously speculated to be incompleteness in realistic devices is the low-visibility conductance oscillation due to unequal beam splitting.

Section: Introductionmentioning

confidence: 99%

Conductance oscillations in Chern insulator junctions: Valley-isospin dependence and Aharonov-Bohm effects

Myoung

Park

2017

“…The presence of short-range scatterers, which cause intervalley scattering, gives rise to additional isospin rotations of the interface states, see Ref. 21.…”

Section: Discussionmentioning

confidence: 99%

“…13, for which the disagreement between simulation and theory is in the range of a few percent only. Without a smoothly vanishing magnetic field at the armchair boundaries, no quantitative agreement between the theoretical predictions (21) and (23) and the numerical simulations could be obtained (data not shown). We note that a significant difference between the theoretical prediction and numerically observed conductance value was previously seen in Ref.…”

Section: Conductance In Ribbon With Mixed Armchair and Zigzag Edgesmentioning

confidence: 97%

Valley isospin of interface states in a graphene pn junction in the quantum Hall regime

Trifunovic

Brouwer

2019

Self Cite

In the presence of crossed electric and magnetic fields, a graphene ribbon has chiral states running along sample edges and along boundaries between p-doped and n-doped regions. We here consider the scattering of edge states into interface states, which takes place whereever the pn interface crosses the sample boundary, as well as the reverse process. For a graphene ribbon with armchair boundaries, the evolution of edge states into interface states and vice versa is governed by the conservation of valley isospin. Although valley isospin is not conserved in simplified models of a ribbon with zigzag boundaries, we find that arguments based on isospin conservation can be applied to a more realistic modeling of the graphene ribbon, which takes account of the lifting of electron-hole degeneracy. The valley isospin of interface states is an important factor determining the conductance of a graphene pn junction in a quantizing magnetic field.

“…Both quantities for the Fano factor have been discussed in the theoretical literature 28,29,38 while experimentally (in Ref. 26 ), only F data are shown.…”

Section: Disorder Effectsmentioning

confidence: 99%

Graphene n−p junctions in the quantum Hall regime: Numerical study of incoherent scattering effects

Parmentier

Roulleau

et al. 2018

We investigate electronic transport through a graphene n-p junction in the quantum Hall effect regime at high perpendicular magnetic field, when the filling factors in the n-doped and p-doped regions are fixed to 2 and -2 respectively. We compute numerically the conductance G, the noise Q and the Fano factor F of the junction when inelastic effects are included along the interface in a phenomenological way, by means of fictitious voltage probes. Using a scaling approach, we extract the system coherence length L φ and describe the full crossover between the coherent limit (W L φ ) and the incoherent limit (W L φ ), W being the interface length. While G saturates at the value e 2 /h in the incoherent regime, Q and F are found to vanish exponentially for large length W . Corrections due to disorder are also investigated. Our results are finally compared to available experimental data.