  We consider a bilayer quantum Hall system at total filling fraction nu=2 in
tilted magnetic field allowing for charge imbalance as well as tunneling
between the two layers. Using an "unrestricted Hartree Fock," previously
discussed by Burkov and MacDonald (Phys Rev B 66 115323 2002), we examine the
zero temperature global phase diagrams that would be accessed experimentally by
changing the in-plane field and the bias voltage between the layers while
keeping the tunneling between the two layers fixed. In accordance with previous
work, we find symmetric and ferromagnetic phases as well as a first order
transition between two canted phases with spontaneously broken U(1) symmetry.
We find that these two canted phases are topologically connected in the phase
diagram and, reminiscent of a first order liquid-gas transition, the first
order transition line between these two phases ends in a quantum critical
point. We develop a physical picture of these two phases and describe in detail
the physics of the transition.
