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arXiv · 1512.07825

Emergence of helical edge conduction in graphene at the ν=0 quantum Hall state

Pavel Tikhonov·Efrat Shimshoni·H. A. Fertig·Ganpathy Murthy
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Abstract

The conductance of graphene subject to a strong, tilted magnetic field exhibits a dramatic change from insulating to conducting behavior with tilt-angle, regarded as evidence for the transition from a canted antiferromagnetic (CAF) to a ferromagnetic (FM) ν=0 quantum Hall state. We develop a theory for the electric transport in this system based on the spin-charge connection, whereby the evolution in the nature of collective spin excitations is reflected in the charge-carrying modes. To this end, we derive an effective field theoretical description of the low-energy excitations, associated with quantum fluctuations of the spin-valley domain wall ground-state configuration which characterizes the two-dimensional (2D) system with an edge. This analysis yields a model describing a one-dimensional charged edge mode coupled to charge-neutral spin-wave excitations in the 2D bulk. Focusing particularly on the FM phase, naively expected to exhibit perfect conductance, we study a mechanism whereby the coupling to these bulk excitations assists in generating back-scattering. Our theory yields the conductance as a function of temperature and the Zeeman energy - the parameter that tunes the transition between the FM and CAF phases - with behavior in qualitative agreement with experiment.

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Pavel Tikhonov, Efrat Shimshoni, H. A. Fertig, Ganpathy Murthy. 2015-12-24. Emergence of helical edge conduction in graphene at the ν=0 quantum Hall state. https://doi.org/10.1103/physrevb.93.115137

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