Finite-temperature transitions in bilayer quantum Hall systems

In this paper, the influence of an in-plane magnetic field (Formula presented) on the transitions at finite temperatures in (Formula presented) bilayer quantum Hall systems is examined. It is found that there can exist two types of characteristic temperatures which separate different regions in the phase diagram. The first is the Kosterlitz-Thouless (KT) transition temperature, which can have an unusual nonmonotonic dependence on (Formula presented) the second type originates from the crossing of energy levels and always increases with (Formula presented) Based on these results, we point out that the threshold temperature observed in the inelastic light scattering experiments cannot be the KT transition temperature, because the latter shows a totally different (Formula presented) dependence as compared with the experimental observation. Instead, it should be the level-crossing temperature, which we found agrees with the (Formula presented) dependence observed. Thus an investigation of the KT transition in the bilayer quantum Hall systems awaits experimental measurements to probe the proposed canted antiferromagnetic phase more directly.