Cascade of Quantum Phase Transitions in Tunnel-Coupled Edge States

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 [Formula presented] is a function of a single scaling argument [Formula presented], where the exponent [Formula presented]. This puzzling resemblance to a quantum Hall-insulator transition points to the importance of interedge correlation between the coupled edge states.