Probing the Extents of Negative Drag in the Quantum Hall Regime

“Negative drag” has been used to describe the reversal of the measured drag voltage when relative densities of the conducting layers are varied in a drag measurement in the quantum Hall regime. Although each layer in the bilayer drag sample contains electrons, the behavior observed mimics that of a system where one layer contains electrons and the other contains holes. While this phenomenon was first observed [1,2] some years ago, we remain without a satisfactory understanding of the effect. An essential element for the elucidation of the basis of this effect remains a clear determination of the experimental conditions under which negative drag is observable, as its existence is destroyed by high fields and temperatures. We report on measurements which characterize these conditions. [1] X. G. Feng et al., Phys. Rev. Lett. 81, 3219 (1998) [2] J. G. S. Lok et al., Phys. Rev. B 63, 041305(R) (2001)