  The natures of the ground state in a $\nu_{\rm T}=1$ bilayer quantum Hall
system at a variety of layer spacing are investigated. At small layer
separations the system exhibits spontaneous interlayer phase coherence. It is
claimed that the Halperin's (1,1,1) state is not relevant in the incompressible
regime near the incompressible to compressible transition point in which the
Josephson-like effect was observed. The two-particle correlation function shows
the deflated correlation hole at this regime. An effective model that can give
a good approximation to the ground state is proposed. A connection to the
modified composite fermion theory is discussed.
