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

Abstract

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.

Manipulation of valley isospins in strained graphene for valleytronics

“…The net phase acquirement of Dirac fermions is calculated by integrating the strain-induced pseudo-magnetic fields over the area enclosed by snake-like trajectories along the junction. 55 Additionally, one can note that G D is independent of h 0 for x 0 ≃ ±6 nm. Such insensitivity to strain is attributed to the fact that the net phase acquirement of Dirac fermions approaches zero (see Supplementary Material for details).…”

“…In this Letter, we consider a gently varying potential profile to allow for practical fabrications in experimental studies. Note that coherent transport through the lowest Landau level (LL) channel is not influenced by the quality of the junction profile 54,55 (see Supplementaty Material for details of the junction profile). For simplicity, the p-n junction is anti-symmetrically produced and only the lowest-LL channels are taken into account.…”

Splitting of conductance resonance through a magnetic quantum dot in graphene

“…10,11,19,20 Such localization is classically understood by snake trajectories of the motion of electrons, which corresponds to quantum Hall interface states at a p-n junction. [21][22][23][24][25][26][27][28] The snake states comprise alternating semicircles with opposite chiralities, so their propagating direction is determined to be one-way along the discontinuous interface. At a circular boundary of magnetic field domains, the snake trajectory of the motion of an electron can result in a closed orbit confining the electronic states within the circular region, a magnetic quantum dot (MQD).…”

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

“…This value also coincides with the original theoretical prediction of Abanin and Levitov 28 , rederived in Refs. 29,38 and confirmed by various numerical works [29][30][31][32][33]43 using different disorder models. 58 However, the fact that various models lead to the same prediction does not allow us to identify the relevant physical mechanisms in play in experiments.…”

“…Numerical studies investigated the role of on-site disorder 29,30 and edge/interface roughness. [31][32][33] Semiclassical snakelike trajectories at the interface were considered as a possible source of mode mixing in the clean limit. 34,35 The full quantum calculation reported in Ref.…”