| I present a theoretical study of dissipative conductance in the zero-plateau quantum Hall state, which appears in undoped Graphene at strong magnetic fields. Charge transport in this state is assumed to be carried by a magnetic domain wall, which forms by hybridization of two counter-propagating edge states of opposing spin in the presence of interactions. The resulting non-chiral edge mode can be modeled as a Luttinger liquid of parameter K, which undergoes a transition to a gapped perfect conductor below a critical value Kc=1/2. The unique spin-charge relation in this system implies that backscattering of charge current must be accompanied by spin-flip, in analogy with phase-slips in superconducting wires. To this end, interaction with localized magnetic moments is included to generate finite resistivity via a "chiral Kondo effect". We find that the resulting resistivity at a finite temperature T may exhibit a crossover from metallic to insulating behavior as K is tuned across a threshold value KMI<1/2. In the insulating regime, the low-T resistivity tends to diverge as K approaches Kc, manifesting a scaling law characteristic of a quantum Kosterlitz-Thouless transition. The model is suggested as a plausible interpretation of recently measured resistive zero-plateau states. |
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