  Multi-wavelength observations suggest that the accretion disk in the hard and
intermediate states of X-ray binaries (XRBs) and active galactic nuclei (AGN)
transitions from a cold, thin disk at large distances into a hot, thick flow
close to the black hole. However, the formation, structure and dynamics of such
truncated disks are poorly constrained due to the complexity of the
thermodynamic, magnetic, and radiative processes involved. We present the first
radiation-transport two-temperature general relativistic magnetohydrodynamic
(GRMHD) simulations of truncated disks radiating at ~35% of the Eddington
luminosity with and without large-scale poloidal magnetic flux. We demonstrate
that when a geometrically-thin accretion disk is threaded by large-scale net
poloidal magnetic flux, it self-consistently transitions at small radii into a
two-phase medium of cold gas clumps floating through a hot, magnetically
dominated corona. This transition occurs at a well-defined truncation radius
determined by the distance out to which the disk is saturated with magnetic
flux. The average ion and electron temperatures in the semi-opaque corona
reach, respectively, T_i ~ 10^10K and T_e ~ 5 10^8K. The system produces
radiation, powerful collimated jets and broader winds at the total energy
efficiency exceeding ~90%, the highest ever energy extraction efficiency from a
spinning black hole by a radiatively efficient flow in a GRMHD simulation. This
is consistent with jetted ejections observed during XRB outbursts. The
two-phase medium may naturally lead to broadened iron line emission observed in
the hard state.
