# What is the broken symmetry in a phase transition into Anderson localisation?

Anderson localisation is a state of matter where there is no diffusion of particles because of randonmness in the potential landscape.
The wavefunction is localised, i.e. exponentially dropping to zero, because of the interference of all the reflected waves from the random potential.

Some experimental groups, i.e. Aspect in Paris as the first one, showed that, by varying the disorder potential $$\Delta$$, one can induce a "phase transition" from an extended (not localised) state to an Anderson localised state.

Can this be called a "phase transition"? What is the broken symmetry between the two regimes?