Open orbits and generalized quantum Hall effect

Abstract
Two-dimensional open-orbit metals can undergo a spin-density-wave transition in a magnetic field which leaves the Fermi energy pinned in a gap. The result for a pure system would be a quantized Hall resistance and vanishing longitudinal resistance. However, in contrast to the closed-orbit case, where impurities are required to observe the quantum Hall effect, in the present case impurities lead to conducting extended states in the gap, Hall plateaus with nonintegral values, and nonvanishing longitudinal resistance.