Are Hall edge currents truly dissipationless?

Question

Integer quantum Hall states has integer number of chiral edge current channels flowing around like supercurrent in a superconductor.

Are they truly dissipationless? If so, what is the mechanism that protects the coupling of different channels or phonon scattering? (e.g. edge current of 2D topological insulator is protected but time-reversal symmetry. But QHS has no symmetry except for particle number conservation and energy conservation.)

Can we roughly estimate the temperature upper bound for a QHS to exist?

Answer 1

If anything, only Hall edge currents are truly dissipationless with or without symmetries, since the edge currents are purely chiral with no back scattering, even in the presence of interaction and magnetic impurities.