Anomalous temperature dependence of electrical transport in quantum Hall multilayers

We study the temperature dependence of vertical transport through the chiral sheath of surface states that exists near the sidewalls of GaAs/Al0.01Ga0.09As multilayer structures in the regime of the integer quantum Hall effect. Because variable-range hopping through the bulk provides a parallel conduction channel, we design our experiment to extend the temperature range of sheath-dominated transport. To do so, we increase device perimeter by using fractal-perimeter mesas. We report on the nearly linear increase of the sheath conductivity with temperature, a result not predicted by existing theories for the edge state sheath.