Abstract
We study single quantum wells and matched density bilayer samples. Simultaneous measurements of the Hall voltages using low frequency lock-in techniques and of the changes in the 232 MHz (12.6 μm) SAW propagation measured with a vector network-analyzer allow comparison of the complex bulk and edge conductivities. The vtotal = 1 bilayer state is seen directly in the SAW measurement only when the conductivity is below ~ 6 × 10−7 Siemens and is destroyed at moderate SAW powers by localized heating. The simultaneous reduction of the conductivity minima extracted from Hall data and from SAW data conclusively demonstrates that the vtotal = 1 state disappears simultaneously throughout the bulk and not by the formation of competing domains or conducting filaments.
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