Cascade of Quantum Phase Transitions in Tunnel-Coupled Edge States

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We report on the cascade of quantum phase transitions exhibited by tunnel-coupled edge states across a quantum Hall line junction. We identify a series of quantum critical points between successive strong and weak tunneling regimes in the zero-bias conductance. Scaling analysis shows that the conductance near the critical magnetic fields Bc is a function of a single scaling argument |B-Bc|T⁻κ, where the exponent κ= 0.42. This puzzling resemblance to a quantum Hall-insulator transition points to importance of interedge correlation between the coupled edge states.