Spin-dependent phase diagram of the νT=1 bilayer electron system

We show that the spin degree of freedom plays a decisive role in the phase diagram of the nu(T)=1 bilayer electron system using an in-plane field B-parallel to in the regime of negligible tunneling. We observe that the phase boundary separating the quantum Hall and compressible states at d/center dot(B)=1.90 for B-parallel to=0 (d: interlayer distance, center dot(B): magnetic length) steadily shifts with B-parallel to before saturating at d/center dot(B)=2.33 when the compressible state becomes fully polarized. Using a simple model for the energies of the competing phases, we can quantitatively describe our results. A new phase diagram as a function of d/center dot(B) and the Zeeman energy is established and its implications as to the nature of the phase transition are discussed.