  We show that in quantum Hall systems at half-filling, edge potentials alone
can drive transitions between the Pfaffian and anti-Pfaffian topological
phases. We conjecture this is true in realistic systems even in the presence of
weak bulk interactions that break the particle-hole symmetry. The strong
effects of edge potentials could be understood from different topological
shifts of competing phases, manifested on the disk geometry as the variation of
orbital numbers at fixed number of particles. In particular, we show
analytically particle-hole conjugation of Hamiltonians on the disk is
equivalent to the tuning of edge potentials, which allows us to explicitly
demonstrate the phase transition numerically. The importance of edge potentials
in various experimental contexts, including the recently discovered
particle-hole symmetric phase is also discussed.
